Cannula with associated filter and methods of use during cardiac surgery

ABSTRACT

Devices and methods for filtering blood. The devices generally comprise a mesh for filtering blood flowing within a blood vessel, particularly within an artery such as the aorta, a structure adapted to open and close the mesh within the blood vessel, and a means to actuate the structure. The methods generally include the steps of introducing a mesh into a blood vessel to entrap embolic material, and removing the mesh and the entrapped foreign matter from the blood vessel.

[0001] This is a continuation of co-pending U.S. application Ser. No.10/006,410, filed Nov. 30, 2001, which is a division of co-pending U.S.application Ser. No. 09/691,641, filed Oct. 18, 2000, now U.S. Pat. No.6,423,086, which is a continuation of co-pending U.S. application Ser.No. 09/455,874, filed Dec. 6, 1999, now U.S. Pat. No. 6,235,045, whichis a continuation of co-pending U.S. application Ser. No. 09/336,372,filed Jun. 17, 1999, now U.S. Pat. No. 6,117,154, which is acontinuation of co-pending U.S. application Ser. No. 08/842,727, filedApr. 16, 1997, now U.S. Pat. No. 5,989,281, which is acontinuation-in-part of U.S. application Ser. No. 08/640,015, filed Apr.30, 1996, now U.S. Pat. No. 5,769,816, which is a continuation-in-partof U.S. application Ser. No. 08/584,759, filed Jan. 11, 1996, nowabandoned, which is a continuation-in-part of U.S. application Ser. No.08/580,223, filed Dec. 28, 1995, now abandoned, which is acontinuation-in-part of U.S. application Ser. No. 08/553,137, filed Nov.7, 1995, now abandoned. Each of the above-identified applications andpatents are expressly incorporated herein by reference in theirentirety.

FIELD OF THE INVENTION

[0002] The present invention relates generally to blood filter devicesfor temporary placement in a blood vessel to capture embolic material,and more particularly to a cannula device having an associated bloodfilter for placement in a blood vessel to carry blood to an artery froma bypass-oxygenator system and to entrap embolic material in the vessel.More particularly, the invention relates to a blood filter device to beplaced in the aorta during cardiac surgery. The present invention alsorelates to methods for temporarily filtering blood to entrap and removeembolic material and, more particularly, to methods for protecting apatient from embolization which has been caused by procedures such asincising, clamping, and clamp release which can dislodge atheromatousmaterial from the artery.

BACKGROUND OF THE INVENTION

[0003] There are a number of known devices designed to filter blood. Thevast majority of these devices are designed for permanent placement inveins, in order to trap emboli destined for the lungs. For example,Kimmell, Jr., U.S. Pat. No. 3,952,747 (this and all other referencescited herein are expressly incorporated by reference as if fully setforth in their entirety herein), discloses the so-calledKimray-Greenfield filter. This is a permanent filter typically placed inthe vena cava comprising a plurality of convergent legs in a generallyconical array, which are joined at their convergent ends to an apicalhub. Each leg has a bent hook at its end to impale the internal walls ofthe vena cava.

[0004] Cottenceau et al., U.S. Pat. No. 5,375,612, discloses a bloodfilter intended for implantation in a blood vessel, typically in thevena cava. This device comprises a zigzagged thread wound on itself anda central strainer section to retain blood clots. This strainer sectioncomprises a meshed net and may be made from a biologically absorbablematerial. This device is also provided with attachment means whichpenetrate into the wall of the vessel.

[0005] Gunther et al., U.S. Pat. No. 5,329,942, discloses a method forfiltering blood in the venous system wherein a filter is positionedwithin a blood vessel beyond the distal end of a catheter by apositioning means guided through the catheter. The positioning means islocked to the catheter, and the catheter is anchored to the patient. Thefilter takes the form of a basket and is comprised of a plurality ofthin resilient wires. This filter can be repositioned within the vesselto avoid endothelialization within the vessel wall.

[0006] Similarly, Lefebvre, French Patent No. 2,567,405, discloses ablood filter for implantation by an endovenous route into the vena cava.The filter is present in the form of a cone, and the filtering means mayconsist of a flexible metallic grid, or a flexible synthetic or plasticgrid, or a weave of synthetic filaments, or a non-degradable or possiblybio-degradable textile cloth. In order to hold the filter within thevein, this device includes flexible rods which are sharpened so thatthey may easily penetrate into the inner wall of the vena cava.

[0007] There are various problems associated with permanent filters. Forexample, when a filter remains in contact with the inner wall of thevena cava for a substantial period of time, endothelialization takesplace and the filter will subsequently become attached to the vena cava.This endothelialization may cause further occlusion of the vessel,thereby contributing to the problem the filter was intended to solve.Except for the Gunther device, these prior art filters do not addressthis problem.

[0008] A temporary venous filter device is disclosed in Bajaj, U.S. Pat.No. 5,053,008. This device treats emboli in the pulmonary artery which,despite its name, is in fact a vein. The Bajaj device is an intracardiaccatheter for temporary placement in the pulmonary trunk of a patientpredisposed to pulmonary embolism because of hip surgery, stroke orcerebral hemorrhage, major trauma, major abdominal or pelvic surgery,neurosurgery, neoplasm, sepsis, cardiorespiratory failure orimmobilization.

[0009] The Bajaj device includes an umbrella made from meshwork whichtraps venous emboli before they reach the lungs. This device can alsolyse emboli with a thrombolytic agent such as tissue plasminogenactivator (TPA), destroy emboli with high velocity ultrasound energy,and remove emboli by vacuum suction through the lumen of the catheter.This very complex device is designed for venous filtration and isdifficult to justify when good alternative treatments exist.

[0010] There are very few intravascular devices designed for arterialuse. A filter that functions not only in veins, but also in arteriesmust address additional concerns because of the hemodynamic differencesbetween arteries and veins. Arteries are much more flexible and elasticthan veins and, in the arteries, blood flow is pulsatile with largepressure variations between systolic and diastolic flow. These pressurevariations cause the artery walls to expand and contract. Blood flowrates in the arteries vary from about 1 to about 5 L/min.

[0011] Ginsburg, U.S. Pat. No. 4,873,978, discloses an arterial device.This device includes a catheter that has a strainer device at its distalend. This device is normally used in conjunction with non-surgicalangioplastic treatment. This device is inserted into the vesseldownstream from the treatment site and, after the treatment, thestrainer is collapsed around the entrapped emboli, and the strainer andemboli are removed from the body. The Ginsburg device could notwithstand flow rates of 5 L/min. It is designed for only small arteriesand therefore could not capture emboli destined for all parts of thebody. For example, it would not catch emboli going to the brain.

[0012] Ing. Walter Hengst GmbH & Co, German Patent DE 34 17 738,discloses another filter which may be used in the arteries of personswith a risk of embolism. This filter has an inherent tension whichconverts the filter from the collapsed to the unfolded state, or it canbe unfolded by means of a folding linkage system. This folding linkagesystem comprises a plurality of folding arms spaced in parallel rowsalong the longitudinal axis of the conical filter (roughly similar tobranches on a tree). The folding arms may be provided with small barbsat their projecting ends intended to penetrate the wall of the bloodvessel to improve the hold of the filter within the vessel.

[0013] Moreover, da Silva, Brazil Patent Application No. P19301980A,discusses an arterial filter for use during certain heart operationswhere the left chamber of the heart is opened. The filter in this caseis used to collect certain particles not removed on cleaning thesurgical site.

[0014] What is needed is a simple, safe blood filter for temporary use.For example, a temporary arterial device for use during surgery thatneither complicates nor lengthens the surgical procedure would bedesirable. Existing prior art devices are inadequate for this purpose.

SUMMARY OF THE INVENTION

[0015] The present invention relates to blood filter devices and methodsof filtering blood.

[0016] The devices of the present invention are adapted to filterembolic material from the blood.

[0017] Embolic material or foreign matter is any particulate matterwhich may cause complications in the body if allowed to travel freely inthe bloodstream. This particulate matter includes but is not limited toatheromatous fragments or material, and fat.

[0018] In one embodiment, the device includes four major elements: amesh, which filters blood flowing in a blood vessel; an insertion tubeadapted for placing the mesh into and removing it from the blood vessel;an umbrella frame adapted for connecting the mesh to the insertion tubeand for positioning and maintaining the mesh in a position wherein bloodpasses therethrough; and a means for opening and closing the umbrellaframe.

[0019] In another embodiment, the device includes three major elements:a mesh, which filters blood flowing in a blood vessel; an umbrella frameadapted for positioning and maintaining the mesh in a position whereinblood passes therethrough; and a means for opening and closing theumbrella frame. The umbrella frame is affixed to a cannula which isinserted into the blood vessel. In alternative embodiments, the meshadditionally may be provided to cover the end of the cannula ifnecessary. This additional mesh simply may be an extension of the meshof the second preferred embodiment, or it may be a separate mesh locatedeither at the end of the cannula or within the cannula.

[0020] In another embodiment, the device includes four major elements: acontinuous mesh for filtering blood flowing within a blood vessel; aninflatable donut-shaped balloon adapted to open and close the mesh; aplurality of tie lines to hold the mesh and balloon in place within thebloodstream; and an actuation assembly. In a preferred embodiment, themesh is cone-shaped and four tie lines attached to the inflatableballoon are employed to hold the balloon and the mesh in place forfiltering.

[0021] In still another embodiment, the device may include an arterialcannula disposed within a pressurizing cannula. The pressurizing cannulahas a proximal region, a distal region, and an intermediate regiontherebetween, which intermediate region includes a first lumen passingfrom the proximal to distal end and shaped to receive a cannula forblood supply. The distal region may include an associated filtercomprising a mesh which may have a substantially conical shape in anexpanded condition and which may be contracted to a smaller,substantially cylindrical shape. The proximal end of the mesh may beattached to an inflatable, donut-shaped balloon or inflation sealadapted to open and close the mesh. The inflation seal-mesh assembly maybe attached at its proximal end to the pressurizing cannula and, at itsdistal end, may optionally include any of an unbroken continuous mesh, amesh attached to a distal region of the cannula for blood supply, and amesh attached to a distal region of the pressurizing cannula. Thepressurizing cannula will generally include means for inflating anddeflating the inflation seal.

[0022] In another embodiment, the device includes a mesh, an arterialcannula, a blood flow diffuser and a structure adapted to open and closethe mesh within the blood vessel, such as an umbrella frame orinflatable balloon. The blood flow diffuser may be located inside oroutside of the arterial cannula. In both the intra-cannula andextra-cannula diffuser embodiments, the flow diffuser can be locatedeither proximal or distal to the mesh.

[0023] In another embodiment, the device includes a sleeve which, whenunrolled, captures the mesh and the expansion frame adapted to open andclose the mesh. In one embodiment the sleeve may be actuated by controllines which control the unrolling and rolling-up of the sleeve. Thecaptured structure may be an umbrella frame adapted for positioning andmaintaining the mesh in a position wherein blood passes therethrough.Alternatively, the captured structure is an inflatable balloon.

[0024] In still another embodiment, the device includes a cannula madein part of a deformable (e.g.) elastomeric material such that thedeformable part of the cannula collapses to absorb the mesh and thecorresponding adapted structure upon mesh closure, thereby reducing theprofile of the instrument for vessel introduction.

[0025] The methods of the present invention relate to filtering bloodflowing within a blood vessel, particularly to entrap embolic material,thereby protecting a patient from embolization. In accordance with oneaspect of the method of the invention, a patient is protected fromembolization during surgery while performing a procedure affecting aregion of an artery of the patient wherein the artery includes foreignmatter on an inside surface thereof at least a portion of which isdislodged as a result of mechanical or other forces applied during theprocedure, by deploying a removable filtration device in a blood vesseldownstream of one affected region of the artery to entrap the dislodgedforeign matter.

[0026] In other embodiments, the methods of the present inventiongenerally include the following steps: introducing a mesh into a bloodvessel to entrap embolic material or foreign matter in the blood,positioning the mesh, if necessary, and removing the mesh and theentrapped foreign matter from the blood vessel. Additionally,visualization techniques including transcranial doppler ultrasonography,transesophageal echocardiography, epicardiac echocardiography, andtranscutaneous or intravascular ultrasonography in conjunction with theprocedure may be used to ensure effective filtration.

[0027] In a preferred method, blood is filtered during cardiac surgery,in particular during cardiac bypass surgery, to protect a patient fromembolization. In this method, the mesh is positioned in the aorta whereit filters blood before it reaches the carotid arteries, brachiocephalictrunk, and left subclavian artery.

[0028] The present invention was developed, in part, in view of arecognition of the occurrence of embolization during cardiac surgery.Emboli are frequently detected in cardiac surgery patients and have beenfound to account for neurologic, cardiac and other systemiccomplications. Specifically, embolization appears to contributesignificantly to problems such as strokes, lengthy hospital stays and,in some cases, death. Of the patients undergoing cardiac surgery, 5-10%experience strokes and 30% become cognitively impaired. In addition, ithas been recognized that embolization is often the result of proceduresperformed on blood vessels such as incising, clamping, and cannulation,wherein mechanical or other force is applied to the vessel. See, forexample, Barbut et al., “Cerebral Emboli Detected During Bypass SurgeryAre Associated With Clamp Removal,” Stroke, 25(12):2398-2402 (1994),which is incorporated herein by reference in its entirety. Theseprocedures are commonly performed in many different types of surgeryincluding cardiac surgery, coronary artery surgery including coronaryartery bypass graft surgery, aneurysm repair surgery, angioplasty,atherectomy, and endarterectomy, including carotid endarterectomy. Ithas also been recognized that reintroducing blood into blood vesselswith a cannula during these procedures can dislodge plaque and otheremboli-creating materials as a result of blood impinging upon the vesselwall at high velocities. See, for example, Cosgrove et. al., LowVelocity Aortic Cannula, U.S. Pat. No. 5,354,288. Finally, it has beenfound that the occurrence of embolization is more likely in certaintypes of patients. For example, embolization occurs more frequently inelderly patients and in those patients who have atheromatosis. In fact,atheromatous embolization, which is related to severity of aorticatheromatosis, is the single most important contributing factor toperioperative neurologic morbidity in patients undergoing cardiacsurgery.

[0029] Embolic material, which has been detected at 2.88 mm in diameter,will generally range from 0.02 mm (20 μm) to 5 mm, and consistspredominantly of atheromatous fragments dislodged from the aortic walland air bubbles introduced during dissection, but also includes plateletaggregates which form during cardiac surgery. See Barbut et al.,“Determination of Embolic Size and Volume of Embolization DuringCoronary Artery Bypass Surgery Using Transesophageal Echocardiography,”J Cardiothoracic Anesthesia (1996). These emboli enter either thecerebral circulation or systemic arterial system. Those entering thecerebral circulation obstruct small arteries and lead to macroscopic ormicroscopic cerebral infarction, with ensuing neurocognitivedysfunction. Systemic emboli similarly cause infarction, leading tocardiac, renal, mesenteric, and other ischemic complications. See Barbutet al., “Aortic Atheromatosis And Risks of Cerebral Embolization,”Journal of Cardiothoracic and Vascular Anesthesia 10(1):24-30 (1996),which is incorporated herein by reference in its entirety.

[0030] Emboli entering the cerebral circulation during coronary arterybypass surgery have been detected with transcranial Dopplerultrasonography (TCD). TCD is a standard visualization technique usedfor monitoring emboli in the cerebral circulation. To detect emboliusing TCD, the middle cerebral artery of a bypass patient iscontinuously monitored from aortic cannulation to bypass discontinuationusing a 2 MHZ pulsed-wave TCD probe (Medasonics-CDS) placed on thepatient's temple at a depth of 4.5 to 6.0 cm. The number of emboli isdetermined by counting the number of embolic signals, which arehigh-amplitude, unidirectional, transient signals, lasting less than 0.1second in duration and associated with a characteristic chirping sound.

[0031] TCD is useful in analyzing the relationship between embolizationand procedures performed on blood vessels. For example, the timing ofembolic signals detected by TCD have been recorded along with the timingof procedures performed during open or closed cardiac surgicalprocedures. One of these procedures is cross-clamping of the aorta totemporarily block the flow of blood back into the heart. It has beenfound that flurries of emboli are frequently detected after aorticclamping and clamp release. During the placement and removal for theclamps, atheromatous material along the aortic wall apparently becomesdetached and finds its way to the brain and other parts of the body.Similarly, flurries of emboli are also detected during aorticcannulation and inception and termination of bypass.

[0032] Transesophageal echocardiography (TEE), another standardvisualization technique known in the art, is significant in thedetection of conditions which may predispose a patient to embolization.TEE is an invasive technique, which has been used, with either biplanarand multiplanar probes, to visualize segments of the aorta, to ascertainthe presence of atheroma. This technique permits physicians to visualizethe aortic wall in great detail and to quantify atheromatous aorticplaque according to thickness, degree of intraluminal protrusion andpresence or absence of mobile components, as well as visualize emboliwithin the vascular lumen. See, for example, Barbut et al., “Comparisonof Transcranial Doppler and Transesophageal Echocardiography to MonitorEmboli During Coronary Bypass Surgery,” Stroke 27(1):87-90 (1996) andYao, Barbut et al., “Detection of Aortic Emboli By TransesophagealEchocardiography During Coronary Artery Bypass Surgery,” Journal ofCardiothoracic Anesthesia 10(3):314-317 (May 1996), and Anesthesiology83(3A):A126 (1995), which are incorporated herein by reference in theirentirety. Through TEE, one may also determine which segments of a vesselwall contain the most plaque. For example, in patients with aorticatheromatous disease, mobile plaque has been found to be the leastcommon in the ascending aorta, much more common in the distal arch andmost frequent in the descending segment. Furthermore, TEE-detectedaortic plaque is unequivocally associated with stroke. Plaque of allthickness is associated with stroke but the association is strongest forplaques over 4 mm in thickness. See Amarenco et al., “Atheroscleroticdisease of the aortic arch and the risk of ischemic stroke,” New EnglandJournal of Medicine, 331:1474-1479 (1994).

[0033] Another visualization technique, intravascular ultrasound, isalso useful in evaluating the condition of a patient's blood vessel.Unlike the other techniques mentioned, intravascular ultrasoundvisualizes the blood vessel from its inside. Thus, for example, it isuseful for visualizing the ascending aorta overcoming deficiencies ofthe other techniques. In one aspect of the invention, it is contemplatedthat intravascular ultrasound is useful in conjunction with devicesdisclosed herein. In this way, the device and visualizing means may beintroduced into the vessel by means of a single catheter.

[0034] Through visualization techniques such as TEE epicardial aorticultrasonography and intravascular ultrasound, it is possible to identifythe patients with plaque and to determine appropriate regions of apatient's vessel on which to perform certain procedures. For example,during cardiac surgery, in particular, coronary artery bypass surgery,positioning a probe to view the aortic arch allows monitoring of allsources of emboli in this procedure, including air introduced duringaortic cannulation, air in the bypass equipment, platelet emboli formedby turbulence in the system and atheromatous emboli from the aorticwall. Visualization techniques may be used in conjunction with a bloodfilter device to filter blood effectively. For example, through use of avisualization technique, a user may adjust the position of a bloodfilter device, and the degree of actuation of that device as well asassessing the efficacy of the device by determining whether foreignmatter has bypassed the device.

[0035] It is an object of the present invention to eliminate or reducethe problems that have been recognized as relating to embolization. Thepresent invention is intended to entrap and remove emboli in a varietyof situations. For example, in accordance with one aspect of theinvention, blood may be filtered in a patient during procedures whichaffect blood vessels of the patient. The present invention isparticularly suited for temporary filtration of blood in an artery of apatient to entrap embolic debris. This in turn will eliminate or reduceneurologic, cognitive, and cardiac complications helping to reducelength of hospital stay. In accordance with another aspect of theinvention, blood may be filtered temporarily in a patient who has beenidentified as being at risk for embolization.

[0036] As for the devices, one object is to provide simple, safe andreliable devices that are easy to manufacture and use. A further objectis to provide devices that may be used in any blood vessel. Yet anotherobject is to provide devices that will improve surgery by lesseningcomplications, decreasing the length of patients' hospital stays andlowering costs associated with the surgery. See Barbut et al.,“Intraoperative Embolization Affects Neurologic and Cardiac Outcome andLength of Hospital Stay in Patients Undergoing Coronary Bypass Surgery,”Stroke (1996).

[0037] The devices disclosed herein have the following characteristics:can withstand high arterial blood flow rates for an extended time;include a mesh that is porous enough to allow adequate blood flow in ablood vessel while capturing mobile emboli; can be used with or withoutimaging equipment; remove the entrapped emboli when the operation hasended; will not dislodge mobile plaque; and can be used in men, women,and children of varying sizes.

[0038] As for methods of use, an object is to provide temporaryfiltration in any blood vessel and more particularly in any artery. Afurther object is to provide a method for temporarily filtering blood inan aorta of a patient before the blood reaches the carotid arteries andthe distal aorta. A further object is to provide a method for filteringblood in patients who have been identified as being at risk forembolization. Yet a further object is to provide a method to be carriedout in conjunction with a blood filter device and visualizationtechnique that will assist a user in determining appropriate sites offiltration. This visualization technique also may assist the user inadjusting the blood filter device to ensure effective filtration. Yet afurther object is to provide a method for filtering blood during surgeryonly when filtration is necessary. Yet another object is to provide amethod for eliminating or minimizing embolization resulting from aprocedure on a patient's blood vessel by using a visualization techniqueto determine an appropriate site to perform the procedure. Anotherobject is to provide a method for minimizing incidence ofthromboatheroembolisms resulting from cannula procedures by coordinatingfiltration and blood flow diffusion techniques in a single device.Another object is to provide a method of passing a filtering devicethrough a vessel wall by first capturing the mesh filter with a sleeveso as to reduce the device profile. For a related discussion of subjectmatter pertaining to a filter cannula, the reader is referred toco-pending U.S. application Ser. No. 08/640,015, filed Apr. 30, 1996,U.S. application Ser. No. 08/584,759, filed Jan. 9, 1996, U.S.application Ser. No. 08/580,223, filed Dec. 28, 1995, and U.S.application Ser. No. 08/553,137, filed Nov. 7, 1995, all of which areexpressly incorporated herein by reference in their entirety.

BRIEF DESCRIPTION OF DRAWINGS

[0039] Reference is next made to a brief description of the drawings,which are intended to illustrate blood filter devices for use herein.The drawings and detailed description which follow are intended to bemerely illustrative and are not intended to limit the scope of theinvention as set forth in the appended claims.

[0040]FIG. 1 is a longitudinal view of a blood filter device accordingto one embodiment.

[0041]FIG. 2 is a longitudinal view of a blood filter device accordingto another embodiment, and in which the device is unsheathed and in anactuation position.

[0042]FIG. 3 is a longitudinal view of a blood filter device depicted inFIG. 2, and in which the device is unsheathed and in a release position.

[0043]FIG. 4 is a longitudinal view of a blood filter device accordingto another embodiment.

[0044]FIG. 5 is a cross-sectional view through section line 5-5 of thedevice depicted in FIG. 4, showing the connection between the balloonand mesh of the device.

[0045]FIG. 6 is a longitudinal view of a blood filter device accordingto another embodiment, showing the filter contracted before deploymentand contained under a retracting handle.

[0046]FIG. 7 is a longitudinal view of the blood filter device depictedin FIG. 6, showing the filter deployed after insertion of the cannulainto the aorta.

[0047]FIG. 8 is a longitudinal view of a flexible arterial cannulashowing standard features which are presently commercially available.

[0048]FIG. 9 is a longitudinal view of a blood filter device accordingto another embodiment, showing the filter deployed after insertion ofthe cannula into the aorta.

[0049]FIG. 10 is a longitudinal view of a blood filter device accordingto another embodiment.

[0050]FIG. 10A is a cross-sectional view through section line I-I of theblood filter device depicted in FIG. 10.

[0051]FIG. 11 is longitudinal view of a cannula with associated filterand distal flow diffuser.

[0052]FIG. 11a is a detail of the flow diffuser of FIG. 11.

[0053]FIG. 12 is a longitudinal view of a cannula with associated filterand distal flow diffuser.

[0054]FIG. 12a is a detail of the flow diffuser of FIG. 12.

[0055]FIG. 13 is a longitudinal view of a cannula with associated filterand proximal flow diffuser.

[0056]FIG. 14 is a longitudinal view of a cannula with associated filterand a proximal flow diffuser.

[0057]FIG. 15 is a longitudinal view of a cannula with associated filteraccording to another embodiment wherein the cannula includes acondom-like filter sleeve shown in a rolled back position.

[0058]FIG. 16 is a longitudinal view of the cannula with associatedfilter of FIG. 15 wherein the unrolled filter sleeve has captured thefilter assembly.

[0059]FIG. 17 shows detail of an unrolled filter sleeve and accompanyingcontrol lines.

[0060]FIG. 18 is a three-dimensional drawing of a cannula withassociated filter with a filter sleeve in the rolled up position.

[0061]FIG. 19 is a longitudinal view of a cannula with associated filterincluding a sleeve deployable by virtue of a pulley mechanism.

[0062]FIG. 20 is a longitudinal view of a cannula with associated filterwherein the cannula has a collapsible section which can accommodate thethickness of the filter.

[0063]FIG. 21 is a longitudinal view of a balloon aortic elastic cannulawherein the cannula's outer diameter and filter profile are reduced byintroduction of a stylet in the cannula's central lumen.

[0064]FIG. 22 is a longitudinal view of the balloon aortic elasticcannula of FIG. 21 wherein the stylet has been withdrawn.

[0065]FIG. 23 is a longitudinal view of a cannula wherein the expanderis proximal to the collapsible portion of the distal cannula.

[0066]FIG. 24 is a longitudinal view of a cannula wherein the expanderhas been inserted into the collapsible portion of the distal cannula.

[0067]FIGS. 25 and 25c depict a cannula wherein the filter has anelasticmeric compliant edge which conforms to vessel irregularities.

[0068]FIGS. 25a, 25 b, and 25 d show other views of the cannula depictedin FIG. 25c.

[0069]FIG. 26 shows a cannula having an open-ended sleeve disposedwithin the aorta.

DETAILED DESCRIPTION

[0070] Referring more particularly to the drawings, FIG. 1 shows oneembodiment of the blood filter device for use herein. The blood filterdevice 10 comprises an insertion tube 20, an umbrella frame 30, and anend plate 60, an activation tube 50, a mesh 40, an adjustment device 70,and a handle 80.

[0071] The device 10 is introduced into a vessel through a main port 7of a cannula 5, and blood or other surgical equipment may be introducedinto the main port 7 of the cannula 5 through a side port 3. The cannula5 and the device 10 will not interfere with placement of equipment whichmay be used during a surgical procedure.

[0072] As shown in FIG. 1, the umbrella frame 30 comprises a pluralityof arms 32 (some of which are not shown), which may include 3 arms, morepreferably 4 arms, more preferably 5 arms, more preferably 6 arms, morepreferably 7 arms, more preferably 8 arms, more preferably 9 arms, andmost preferably 10 arms. The arms are sonically welded to a socket 34,which in turn is adhesive bonded to the insertion tube 20 which isdimensioned to fit within the main port 7 of the cannula 5 withoutunnecessarily impeding blood flow. Alternatively, the socket 34 may beconnected to the insertion tube 20 by welding or epoxy. The insertiontube 20 is made of commercially available material such as polyvinyl,clear PVC, polyurethane, or other plastics. The arms 32 of the umbrellaframe 30 are made of plastic or thin gage metal. Because of theflexibility of this material, the arms 32 bend without the need forextra parts such as hinges. This simplifies assembly and reduces thechances of misassembly. Each of the arms 32 is provided with an undercutto facilitate bending. Alternatively, the arms 32 may be made of amaterial having a shape memory characteristic, causing the arms to bendin the absence of external forces. A silicone material may be attachedto the arms at the point at which they bend to act as a shock absorber.Alternatively, the arms may be coated with a hydrophilic coating orother shock absorbing material. Although the frame includes eight armsin one preferred embodiment, it is also contemplated that the umbrellaframe may comprise more or less than eight arms.

[0073] The end plate 60 comprises a one-piece injection moldedcomponent, made of plastics or metal. The end plate 60 is substantially0-shaped with a radius r and indent in the center of the O-shape. Theeight arms 32 of the umbrella frame 30 are sonic welded or bonded to theend plate 60 at eight arm junctures 61 spaced in 45 degree incrementsalong a circumference of a circle defined by radius less than r. Theactivation tube 50 is welded or attached with epoxy to the indent 62.

[0074] The activation tube 50 extends from the end plate 60, through theinsertion tube 20, to the adjustment device 70 housed in the handle 80as shown in FIG. 1. The adjustment device 70 is a linear actuationdevice, comprising a thumb switch 72 which is attached to a guide frame74 which in turn is attached to the activation tube 50 via a bond joint.Thumb switch 72 comprises a base 76 and a ratchet arm 78 which movesalong a ratchet slot 82 along the top of the handle 80, locking inpredetermined intervals in a manner known in the art. Sliding the thumbswitch 72 away from the distal end 2 of the cannula 5 retracts theactivation tube 50, which in turn draws the end plate 60 toward thehandle 80. This causes the arms 32 of the umbrella frame 30 to bend andthe mesh 40 to open and ready to trap foreign matter in the blood.Sliding thumb switch 72 toward the distal end 2 of the cannula 5 pushesthe activation tube 50 in the direction of the mesh 40. The activationtube 50 then pushes the end plate 60 away from the handle 80, causingthe arms 32 of the umbrella frame 30 to straighten and the mesh 40 toclose.

[0075] If, in the alternative, the arms 32 of the umbrella frame 30 aremade of a material with a shape memory characteristic, the linearactuation device must include a locking mechanism which, when locked,maintains the arms 32 in a straight position and which, when released,allows the arms 32 of the umbrella frame 30 to bend.

[0076] Other linear actuation devices known in the art also may beincorporated into the present invention such as, but not limited to, afriction fit slot device with a nub on the end, a device whichincorporates hydraulic pressure or an electromechanical device with amotor.

[0077] To filter blood effectively, i.e., to entrap embolic material,without unduly disrupting blood flow, the mesh must have the appropriatephysical characteristics, including area (A_(M)), thread diameter(D_(T)), and pore size (S_(P)). In the aorta, the mesh 40 must permitflow rates as high as 3 L/min or more, more preferably 3.5 L/min ormore, more preferably 4 L/min or more, more preferably 4.5 L/min ormore, more preferably 5 L/min or more preferably 5.5 L/min or more, andmost preferably 6 L/min or more at pre-arterial pressures of around 120mm Hg or less.

[0078] In order to entrap as many particles as possible, mesh with theappropriate pore size must be chosen. The dimensions of the particles tobe entrapped are an important factor in this choice. In the aorta, forexample, particle size has been found to range from 0.27 to 2.88 mm.with a mean of 0.85 mm, and particle volume has been found to range from0.01 to 12.45 mm³, with a mean of 0.32 mm³. Approximately 27 percent ofthe particles have been found to measure 0.6 mm or less in diameter.During cardiac bypass surgery in particular, aortic embolic load hasbeen found to range from 0.57 cc to 11.2 cc, with a mean of 3.7 cc, andan estimated cerebral embolic load has been found to range from 60 to510 mm³, with a mean of 276 mm³.

[0079] When a bubble greater than 100 μm diameter encounters the filter,there must be sufficient pressure on the proximal side of the filter toforce the bubble through the pore. The surface tension of the bloodgenerally prevents the bubble from deforming and extruding through thepore, but rather the bubble breaks apart into a plurality of bubblessmall enough to pass freely through the pore. The filter thereby acts asa bubble sieve.

[0080] The benefit of reducing the size of the interactive bubbles istwofold. First, the potential of a bubble to cause ischemia is directlyrelated to its diameter. The larger the bubble, the more likely it is toblock blood flow to a larger area of the brain. Smaller bubbles mayblock smaller arteries, but will have less overall ischemic effect.Second, smaller bubbles will be absorbed into tissue and cells morequickly than large bubbles, because of their greater surface area tovolume ratio. The net effect is smaller bubbles which may make their wayinto the brain, and bubbles which will be more quickly metabolizedfurther reducing risk of embolic ischemia.

[0081] Another method by which large bubbles can be rendered intosmaller bubbles is due to velocity and momentum effects. During momentsof peak systolic cardiac output, the blood velocity from the heart is atits maximum (100-150 cm/s). If a bubble is trapped against theintra-aortic filter and is subject to instantaneous high velocity bloodflow, the momentum of the blood on the bubble will cause the bubble toshatter into smaller bubbles. The smaller bubbles will then “escape”through the pores in the filter if they have been rendered small enough.

[0082] By way of example, when a device of the present invention isintended for use in the aorta, the area of the mesh required for thedevice 10 is calculated in the following manner. First, the number ofpores N_(P) in the mesh is calculated as a function of thread diameter,pore size, flow rate, upstream pressure and downstream pressure. This isdone using Bernoulli's equation for flow in a tube with an obstruction:${\frac{P_{1}}{\rho*g} + \frac{V_{1}^{2}}{2*g}} = {\frac{P_{2}}{\rho*g} + {\frac{V_{2}^{2}}{2*g}*A}}$

[0083] In this equation, P is pressure, ρ is density of the fluid, g isthe gravity constant (9.8 m/s²), V is velocity, K represents the lossconstants, and f is the friction factor. The numbers 1 and 2 denoteconditions upstream and downstream, respectively, of the filter.

[0084] The following values are chosen to simulate conditions within theaorta:

[0085] P₁=120 mm Hg;

[0086] P₂=80 mm Hg;

[0087] K_(entry)=0.5;

[0088] K_(exit)=1.0;

[0089] K=K_(entry)+K_(exit); and$\left\lbrack \frac{Dr}{S_{P}} \right\rbrack_{Equiv}$

[0090] is 30.

[0091] Assuming laminar flow out of the mesh filter, f is given as$\frac{64}{Re}$

[0092] where Re is the Reynold's number and the Reynold's number isgiven by the following equation:${Re} = \frac{\left( {\rho*Q*S_{P}} \right)}{\left( {\mu*N_{P}*A_{h}} \right)}$

[0093] where μ is the kinematic viscosity of the fluid and A_(h) is thearea of one hole in the mesh given by S_(P)*S_(P).

[0094] Conservation of the volume dictates the following equation:${N_{P}*V_{2}*A_{h}} = {{Q\quad {OR}\quad V_{2}} = \frac{Q}{\left( {N_{P}*A_{h}} \right)}}$

[0095] where Q is the flow rate of the blood. In addition, V₁ is givenby: $V_{1} = \frac{Q}{A_{vessel}}$

[0096] where A_(vessel) is the cross-sectional area of the vessel.Substitution and manipulation of the above equations yields N_(P).

[0097] Next, the area of the mesh is calculated as a function of thenumber of pores, thread diameter and pore size using the followingequation:

A _(M) =N _(P)*(D _(T) +S _(P))²

[0098] In an embodiment of the device 10 that is to be used in theaorta, mesh with dimensions within the following ranges is desirable:mesh area is 3-10 in², more preferably 4-9 in², more preferably 5-8 in²,more preferably 6-8 in², most preferably 7-8 in²; mesh thickness is20-280 μm, more preferably 23-240 μm, more preferably 26-200 μm, morepreferably 29-160 μm, more preferably 32-120 μm, more preferably 36-90μm, more preferably 40-60 μm; thread diameter is 10-145 μm, morepreferably 12-125 μm, more preferably 14-105 μm, more preferably 16-85μm, more preferably 20-40 μm; and pore size is 50-300 μm, morepreferably 57-285 μm, more preferably 64-270 μm, more preferably 71-255μm, more preferably 78-240 μm, more preferably 85-225 μm, morepreferably 92-210 μm, more preferably 99-195 μm, more preferably 106-180μm, more preferably 103-165 μm, more preferably 120-150 μm. In apreferred embodiment of the invention, mesh area is 3-8 in², meshthickness is 36-90 μm, thread diameter is 16-85 μm, and pore size is103-165 μm. In a further preferred embodiment of the invention, mesharea is 3-5 in², mesh thickness is 40-60 μm, thread diameter is 20-40μm, and pore size is 120-150 μm.

[0099] The calculation set forth above has been made with reference tothe aorta. It will be understood, however, that blood flow parameterswithin any vessel other than the aorta may be inserted into theequations set forth above to calculate the mesh area required for ablood filter device adapted for that vessel.

[0100] To test the mesh under conditions simulating the conditionswithin the body, fluid flow may be observed from a reservoir through apipe attached to the bottom of the reservoir with the mesh placed overthe mouth of the pipe through which the fluid exits the pipe. A mixtureof glycerin and water may be used to simulate blood. Fluid height (h) isthe length of the pipe in addition to the depth of the fluid in thereservoir, and it is given by the following equation:$h = \frac{P}{\left( {\rho*g} \right)}$

[0101] where ρ is given by the density of the glycerin-water mixture,and g is given by the gravity constant (9.8 ms²).

[0102] Bernoulli's equation (as set forth above) may be solved in orderto determine (D_(T)/S_(P))_(Equiv). V₁ is given by the followingequation: $V_{1} = \frac{Q}{A_{1}}$

[0103] where Q is the flow rate which would be measured during testingand A₁ is the cross-sectional area of the pipe. V₂ is given by thefollowing equation: $V_{2} = \frac{Q}{\left( {N*A_{2}} \right)}$${Re} = \frac{\left( {\rho*V_{2}*D} \right)}{\mu}$

[0104] where N is the number of pores in the mesh and A₂ is the area ofone pore. Further, P₁=120 mm Hg and P₂=0 mm Hg and S_(P) is the diagonallength of the pore. Reynold's number (Re) is given by the followingequation:

[0105] where ρ and μ are, respectively, the density and kinematicviscosity of the glycerin-water mixture.

[0106] Once appropriate physical characteristics are determined,suitable mesh can be found among standard meshes known in the art. Forexample, polyurethane meshes may be used, such as Saati and Tetkomeshes. These are available in sheet form and can be easily cut andformed into a desired shape. In a preferred embodiment, the mesh issonic welded into a cone shape. Other meshes known in the art, whichhave the desired physical characteristics, are also suitable. The mesh40 is sonic welded or adhesive bonded to the arms 32 of he umbrellaframe 30 from the end plate 60 to a point on each arm 32 between the endplate 60 and the socket 34 as shown in FIG. 1. This is the optimalplacement of the Mesh 40 when the device 10 is inserted into the vesselin the direction of the blood flow. However, it is also contemplatedthat the device 10 may be inserted in a direction opposite the bloodflow. In this case, the mesh 40 would be attached to the arms 32 of theumbrella frame 30 from the socket 34 to a point on each arm 32 betweenthe socket 34 and the end plate 60.

[0107] Anticoagulants, such as heparin and heparinoids, may be appliedto the mesh 40 to reduce the chances of blood clotting on the mesh 40.Anticoagulants other than heparinoids also may be used. Theanticoagulant may be painted or sprayed onto the mesh. A chemical dipcomprising the anticoagulant also may be used. Other methods known inthe art for applying chemicals to mesh may be used.

[0108] The device 10 may be used in the following manner. A cannula 5 isintroduced into the vessel through an incision made in the vessel wall,and the cannula 5 is then sutured to the vessel wall. The cannula 5 ispreferably size 22-25 French (outer diameter). The blood filter device10 is then inserted into the vessel through the cannula 5. Within thecannula 5, the blood filter device 10 is maintained in a releaseposition in which the arms 32 of the umbrella frame 30 are straight andthe mesh 40 is closed. (See FIG. 3.)

[0109] In order to actuate the device 10, the surgeon slides the thumbswitch 72 of the adjustment device 70 along the ratchet slot 82, awayfrom the distal end 2 of the cannula 5, until an appropriate actuationposition is achieved or until the mesh 40 is opened to its maximum size.(See FIG. 2.) The arms 32 may bend to varying degrees in a plurality ofactuation positions, and the appropriate actuation position depends onthe cross-sectional dimension of the blood vessel. During filtration, auser may gently palpate the outside of the blood vessel to feel pointsof contact between the vessel wall and the device 10. This enables theuser to determine the appropriate actuation position and the location ofthe device within the vessel.

[0110] When filtration has been completed, the user slides the thumbswitch 72 toward the distal end 2 of the cannula 5, thereby effectingthe release position, in which the arms 32 of the umbrella frame 30straighten and the mesh 40 closes around the captured emboli. (See FIG.3.) The handle 80 may be additionally provided with a marker band whichmatches up with a corresponding marker band on the thumb switch 72 whenthe device 10 is in the release position. The device 10 is pulled backinto the cannula 5, and then cannula 5 and the device 10, along with thecaptured emboli, are removed from the body.

[0111] In another embodiment, a blood filter device is provided asillustrated in FIGS. 2 and 3. The device 10 comprises an introducer 103,a cannula 105, having a distal end 111, a sheath 120, an umbrella frame130, an annular mesh 140, a movable ring 150, a fixed ring 160,guidewires 170, and a clam-shell handle 180.

[0112] The introducer 103 comprises a cylinder 107 and an adjustablesuture ring 109. The cylinder 107 of the introducer 103 is made to fitaround the sheath 120, which slides over the cannula 105 and theguidewires 170.

[0113] The umbrella frame 130 is substantially similar to the umbrellaframe 30 depicted in FIG. 1. The umbrella frame 130 comprises aplurality of arms 132 (some of which are not shown) as discussed abovewith reference to FIG. 1, which arms are connected at one end (of eacharm 132) to the fixed ring 160 and at the other end (of each arm 132) tothe movable ring 150. The fixed ring 160 is firmly secured to thecannula 105. Each guidewire 170 is firmly secured at one end to themovable ring 150 m, which slides along the outer surface of the cannula105, and at the other end to the clamshell handle 180, which is a linearactuation device known in the art.

[0114] The mesh 140 must entrap embolic material without undulydisrupting blood flow. This mesh 140 also may be found among standardmeshes known in the art. The same analysis used to select and test themesh 40 of the first preferred embodiment may be used to select the mesh140.

[0115] The device 10 is used in the following manner. The device 10 isinserted into the blood vessel. The sheath 120 is retracted until itexposes the umbrella frame 130. A user effects the actuation position bypushing the movable ring 150 toward the fixed ring 160 via theclam-shell handle 180 and the guidewires 170 as shown in FIG. 2. In theactuation position, the arms 132 of the umbrella frame 130 are bent andthe annular mesh 140 is open and ready to capture foreign matter in theblood.

[0116] In order to remove the blood filter 10 from the body, the userfirst pulls the movable ring 150 away from the fixed ring 160 via theclamshell handle 180 and the guidewires 170. This causes the arms 132 ofthe umbrella frame 130 to straighten and the annular mesh 140 to close,trapping the emboli against the cannula 105. The user then removes theblood filter device 10 from the body along with the captured emboli.Alternatively, the user may first slide the sheath 120 back over thecannula 105, and then remove the device 10 from the body along with thecaptured emboli.

[0117] In an alternative embodiment adapted for use in the aorta duringcardiac surgery, a second mesh may be placed over the distal end 111 ofthe cannula 105 or within the cannula 105 so that blood flowing into thebody from an extracorporeal source is also filtered. Alternatively, inlieu of an annular mesh 140 and a second mesh, a single mesh may be usedwhich is configured such that it covers the distal end 111 of thecannula 105.

[0118] An advantage of the embodiment depicted in FIG. 2 is that it doesnot require a cannula with a separate port for the introduction of bloodor a surgical equipment.

[0119]FIG. 4 shows another embodiment of the blood filter devicedisclosed herein. As shown in FIG. 4, the blood filter device 10comprises a mesh 220, an inflatable balloon 230, a collar 240, aplurality of tie lines 250, and an actuation assembly 260. The mesh 220is attached to the balloon 230 via the collar 240. In use, the device 10is positioned and maintained in a blood vessel via the plurality of tielines 250. Manipulation of actuation assembly 260 inflates and deflatesthe balloon 230 and controls the degree of inflation and deflation.Inflation of the balloon 230 opens the mesh 220, and deflation of theballoon 230 allows the mesh 220 to close.

[0120] Mesh 220, found among standard meshes as in the first twoembodiments, should cover substantially all of the cross-sectional areaof a vessel so that blood flowing in the vessel must pass through themesh 220. In this way, foreign matter in blood within the vessel isentrapped by the mesh 220. In the preferred embodiment, the mesh 220 isgenerally cone-shaped. However, the shape of the mesh 220 may bemodified to assume any shape as long as blood flowing in the vesselpasses through the mesh 220.

[0121] As shown in FIG. 4, inflatable balloon 230 is attached to themesh 220 via the collar 240. In a preferred embodiment, the balloon 230is made of two pieces of a flexible, slightly porous material such asurethane or polyethylene terephalate (PET), each piece having an outerdiameter and an inner diameter. These pieces are welded together at boththe outer and inner diameters in a manner known in the art. The balloon230 also has a valve 268 and a valve stem 266 located between the outerdiameter and the inner diameter of the balloon 230. Material used forthe balloon 230 must be capable of inflation and deflation. It also mustbe sufficiently flexible to conform to the walls of a vessel regardlessof possible irregularities in the walls, such as may be caused by plaqueor other materials adhering to the walls. Material used for the balloon230 also must be sufficiently flexible to allow the balloon 230 to foldup within a cannula 205. Exemplary materials include elastomeric andcertain non-elastomeric balloons.

[0122] To inflate the balloon 230 and thereby open the mesh 220, a fluidor a gas, is introduced into the balloon 230 through the valve 268. Todeflate the balloon 230, the fluid or gas is removed from the balloon230 through the valve 268. Fluids such as saline may be used, and gasessuch as inert gases may be used with this invention. Any fluid or gasmay be used as long as it does not harm the patient if released into thebloodstream. The saline or other suitable inflation material istypically stored in a reservoir outside the body, which is capable offluid communication with the balloon 230 through a tube 264.

[0123] In an embodiment of the devices suited for placement in theaorta, the balloon 230 has an outer diameter of approximately 100 Fr.,more preferably 105 Fr., more preferably 110 Fr., more preferably 115Fr., more preferably 120 Fr., and most preferably 125 Fr., or greater,and an inner diameter of approximately 45 Fr. (1 Fr.=0.13 in.) whenfully inflated. The dimensions of the balloon 230 may be adjusted inalternative embodiments adapted for use in vessels other than the aorta.Alternatively, expandable members other than a balloon also may be usedwith this invention.

[0124] Referring to FIG. 4, the collar 240 is attached to the outerdiameter of the balloon 230 and is a generally circular piece ofplastic. Other materials, such as silicone or high density polyethylenemay be used. This material should be rigid enough to withstand flowconditions in blood vessels, yet flexible enough to expand as theballoon 230 is inflated and to fold up as the balloon 230 is deflatedand stored within the cannula 205. The collar 240 has both an inner andouter diameter, and the outer diameter is bent slightly outward. Asshown in FIG. 5, the collar 240 is attached to the outer diameter of theballoon 230 by welding, adhesive or other attachment means known in theart. The mesh 220, in turn, is adhesive bonded to the collar 240.Alternatively, the mesh 220 may be connected to the collar 240 bywelding, epoxy, or other suitable adhesive means.

[0125] Actuation of the device 10 is accomplished by the actuationassembly 260, which inflates and deflates the balloon 230 by introducinginto and removing from the balloon 230 the fluid or gas. The actuationassembly 260 also controls the degree to which the mesh is opened withinthe blood vessel. The actuation assembly 260 may be used to adjust thefit of the device 10 within the vessel during filtration or use of thedevice 10. In addition, because the degree to which the mesh is openedmay be adjusted by the actuation assembly 260, one embodiment of thedevice may be suitable for a variety of vessel sizes.

[0126] Actuation assembly 260 comprises an inflation catheter 262 andthe tube 264 which is connected to the valve stem 266. The inflationcatheter 262 is preferably 9 F.O.D. and is marked in cubic centimeterincrements in order to monitor the degree to which the balloon 230 isinflated. The tube 264 is preferably size 12 Fr.O.D. and 7.2 Fr.I.D.

[0127] A plurality of tie lines 250, which may include three tie lines,four tie lines, or more than four tie lines, position and maintain thedevice 10 in place in the bloodstream. The tie lines 250 are made ofwire and are threaded through the balloon 230 at points equally spacedalong the inner diameter of the balloon, e.g., for four tie lines thefour points are space 90 degrees apart along the inner diameter of theballoon 230. The tie lines 250 may be made of other materials havingsufficient stiffness to push and pull the balloon 230 out of and intothe cannula 205 and to maintain the device 10 within the blood vessel.

[0128] All components of this device should be composed of materialssuitable for insertion into the body. Additionally, sizes of allcomponents are determined by dimensional parameters of the vessels inwhich the devices are intended to be used. These parameters are known bythose skilled in the art.

[0129] By way of purely illustrative example, the operationalcharacteristics of a filter according to the invention and adapted foruse in the aorta are as follows: Temperature Range 25-39 degrees C.Pressure Range 50-120 mm Hg Flow Rate usually up to 5 L/min., can be ashigh as 6 L/min. Duration of single use up to approximately 5 hoursAverage emboli trapped  5-10,000 Pressure gradient range(100-140)/(50-90)

[0130] Modification of the operational characteristics set forth abovefor use of the present invention in vessels other than the aorta arereadily ascertainable by those skilled in the art in view of the presentdisclosure.

[0131] An advantage of all embodiments disclosed herein is that theblood filter will capture emboli which may result from the incisionthrough which the blood filter is inserted.

[0132] In use, there are a number of methods for protecting patientsfrom embolization and for filtering blood using the devices disclosedherein. Temporary filtration is frequently required in association withprocedures performed on blood vessels because there is a possibility ofembolization associated with such procedures. For example, there is acorrelation between embolization and the aortic clamping and unclampingwhich is performed during cardiac bypass surgery.

[0133] The devices of the present invention are particularly suited foruse in methods of the present invention. However, other devices may beadapted for use in accordance with the methods of the present invention.

[0134] The methods of the present invention generally include thefollowing steps: introducing a blood filter device into a blood vesselof a patient to entrap embolic matter or foreign matter in the blood;and removing the mesh and the entrapped foreign matter from the bloodvessel. The blood filter device also may be adjusted if this isnecessary during the course of filtration.

[0135] In addition, use of visualization techniques is also contemplatedin order to determine which patients require filtration (identify riskfactors), where to effectively position a blood filter device tomaximize effectiveness, when to adjust the device if adjustment isnecessary, when to actuate the device and appropriate regions forperforming any procedures required on a patient's blood vessel.

[0136] According to one method of the present invention, the bloodfilter device depicted in FIGS. 4 and 5 is introduced into a patient'sblood vessel. Typically, an incision is first made in a vessel of apatient, and, with reference to FIG. 4, cannula 205 is introduced intothe incision in the direction of blood flow. Within the cannula 205, thedevice 10 is stored in a closed position in which the balloon isdeflated and generally folded in upon itself and the mesh 220 is closed.

[0137] The blood filter device 10 is then pushed out through the cannula205 into the vessel by pushing the tie lines 250 in the direction ofblood flow. To actuate the device 10, the actuation assembly 260inflates the balloon until the balloon 230 opens the mesh 220 within thevessel to cover substantially all of the cross-sectional area of thevessel such that blood flowing through the vessel flows through the mesh220. As the blood flows through the mesh 220, foreign matter isentrapped by the mesh.

[0138] When the filter is no longer needed, the device 10 is removedfrom the vessel along with the entrapped foreign matter. The balloon 230is deflated, and the tie lines 250 are pulled toward the cannulaopposite the direction of the blood flow. As the balloon 230 is pulledinto the cannula 205, the balloon 230 folds in upon itself, and the mesh220 closes around the entrapped foreign matter. In an alternativeembodiment, the cannula 205 may be configured to further accommodateentry of the balloon 230, the mesh 220, and the entrapped foreign matterinto the cannula 205 without disturbing blood flow. For example, the endof the cannula placed within the vessel may be very slightly flared.

[0139] In accordance with one aspect of the invention, a visualizationtechnique, such as TCD, is used to determine when to actuate a bloodfilter device. For example, during cardiac bypass surgery, flurries ofemboli are detected during aortic cannulation, inception, andtermination of bypass and cross-clamping of the aorta. Therefore, a meshmay be opened within a vessel downstream of the aorta during theseprocedures and closed when embolization resulting from these procedureshas ceased. Closing the mesh when filtration is not required helps tominimize obstruction of the blood flow.

[0140] According to another embodiment, a visualization technique isused to monitor emboli entering cerebral circulation to evaluate theeffectiveness of a blood filter device in trapping emboli. Also, avisualization technique is useful to positioning a device within avessel so that it operates at optimum efficiency. For example, a usermay adjust the position of the device if TCD monitoring indicates emboliare freely entering the cerebral circulation. In addition, a user mayadjust a mesh of a blood filter device to ensure that substantially allof the blood flowing in the vessel passes through the mesh.

[0141] According to yet another embodiment, a visualization technique,such as TEE and epicardial aortic ultrasonography, is used to identifythose patients requiring blood filtration according to the presentinvention. For example, these visualization techniques may be used toidentify patients who are likely to experience embolization due to thepresence of mobile plaque. These techniques may be used before thepatient undergoes any type of procedure which will affect a blood vesselin which mobile plaque is located.

[0142] Additionally, visualization techniques may be used to selectappropriate sites on a blood vessel to perform certain procedures toeliminate or reduce the occurrence of embolization. For example, duringcardiac bypass surgery, the aorta is both clamped and cannulated. Theseprocedures frequently dislodge atheromatous material already present onthe walls of the aorta. To minimize the amount of atheromatous materialdislodged, a user may clamp or cannulate a section of the aorta whichcontains the least amount of atheromatous material, as identified byTEE, epicardial aortic ultrasonography or other visualization technique.

[0143] Procedures other than incising and clamping also tend to dislodgeatheromatous material from the walls of vessels. These proceduresinclude, but are not limited to, dilatation, angioplasty, andatherectomy.

[0144] Visualization techniques also may be used to select appropriatesites for filtering blood. Once atheromatous material is located withina vessel, a blood filter device may be placed downstream of thatlocation.

[0145] Visualization techniques, other than those already mentioned, asare known to those skilled in the art, are also useful in ascertainingthe contours of a blood vessel affected by surgical procedure to assessa variety of risk of embolization factors, and to locate appropriatesections of a vessel for performing certain procedures. Any suitablevisualization device may be used to evaluate the efficacy of a device,such as those disclosed herein, in trapping emboli.

[0146] In another embodiment, a cannula with associated filter isprovided as depicted in FIGS. 6 and 7. With reference to FIG. 6, thedevice includes a pressurizing cannula 300 having proximal region 301,distal region 302, and an intermediate region which connects theproximal and distal regions. The pressurizing cannula 300 is typically arigid or semi-rigid, preferably transparent tube having a firstsubstantially cylindrical lumen 303 which extends from the proximalregion to the distal region and is shaped to receive blood supplycannula 350. The pressurizing cannula 300 further includes at itsproximal region luer fittings 304 and 305 which are shaped to receive acap or septum 306 and a syringe 307 filled with saline or gas and havinga locking mechanism 308 (FIG. 7) for locking the barrel 309 and plunger310 in a fixed position. The pressurizing cannula 300 typically has adual lumen to effect pressurization of the inflation seal (discussedbelow). Thus luer 305 is connected to passage 311 which is in fluidcommunication with a second lumen 312 which extends from the proximal tothe distal end of pressurizing cannula 300. Meanwhile, luer 304 isconnected to passage 313 which is in fluid communication with a thirdlumen 314 which extends from the proximal to the distal end ofpressurizing cannula 300. At its distal region, the pressurizing cannula300 includes a blood filtration assembly 315 which is shown in greaterdetail in FIG. 7.

[0147]FIG. 8 depicts a standard flexible arterial cannula 400 which iscommercially available from Sarns 3M (Ann Arbor, Michigan). Withreference to FIG. 8, the cannula will typically have a length of about25 cm. The cannula includes a distal end region 401, a proximal endregion 402, and an intermediate region disposed therebetween. Distal endregion 401 has an outer diameter of about 8 mm, and a sealing ring 403having an enlarged diameter of about 13 mm, a width of about 5 mm, andbeing disposed about 25 mm from the distal tip of cannula 400. Sealingring 403 functions as an anchor point against the inside of an aorticincision so that cannula 400 does not slide from the aorta during aprocedure. Proximal end region 402 includes a connector 404 which joinsthe cannula to the blood machine. At its proximal tip, the cannulaincludes a tapered joint 405 which connects and locks the cannula to abypass-oxygenator machine.

[0148] Referring again to FIG. 6, blood supply cannula 350 may havecertain features in common with the standard cannula 400 depicted inFIG. 8. Blood supply cannula 350 for use herein is a substantiallycylindrical, semi-rigid, and preferably transparent tube which includesa rib 351 disposed about the circumference at a distal region thereof.The blood cannula is slideable within the pressurizing cannula, and inthe proximal region, the blood cannula 350 may be angled to adopt ashape which does not interfere with syringe 307. Moreover, the bloodcannula will typically include a fitting or molded joint 352 which isadapted for coupling to a bypass-oxygenator system. Blood cannula 350 isadapted to carry blood to the aorta from the bypass-oxygenator system.

[0149] The pressurizing cannula may also include an inserting andretracting handle 380 comprising a substantially cylindrical tubedisposed about the intermediate region of pressurizing cannula 300.Handle 380 will generally include a rigid or semi-rigid, preferablytransparent tube with molded hand grip to facilitate holding andinserting. With reference to FIG. 7, handle 380 is slideable relative tothe pressurizing cannula 300, and may include a sealing member 381comprising a rubber washer or O-ring mounted in a proximal region of thehandle and disposed between handle 380 and pressurizing cannula 300 toprevent leakage of blood therebetween. Handle 380 may includecorrugation ribs 382 and its proximal and intermediate regions, and asubstantially flat or level collar insertion region 383 adapted to fittightly against vessel material at an aortic incision. In certainembodiments, the collar insertion region 383 will include a sealing ringor rib (not shown), having a width of about 5 mm and an outer diameterof about 13 mm, which serves as an anchor against the aorta to preventthe cannula assembly from slipping out during a surgical procedure. A“purse string” suture is generally tied around the circumference of theaortic incision, and this string will be tightened around the ring incollar region 383 to prevent slippage of the cannula assembly.

[0150] Handle 380 may also include an enlarged end region 384 whichencloses the blood filtration assembly 315 as depicted before insertionin FIG. 6. This housing enclosure 384 is a particularly preferredcomponent because it prevents inadvertent deployment of the bloodfiltration assembly, and it provides a smooth outer surface to thecannula which facilitates entry through an incision in the aorta withouttearing the aorta. In the absence of such housing enclosure, the balloonand filter are liable to scrape against the inner wall of a vessel, andthereby damage or rupture the vessel. At its distal end, handle 380 mayinclude inverted cuff 385 which bears against rib 351 of blood cannula350 to form a seal when the filtration assembly 315 is enclosed inhandle 380.

[0151] With reference to FIG. 7, the distal region of pressurizingcannula 300 is shown with blood filtration assembly 315 deployed in theascending region of a human aorta 399. Handle 380 has been movedproximally to expose filter assembly 315. The distal region ofpressurizing cannula 300 includes a plurality of spokes or holdingstrings 316 made from Dacron™ or other suitable material. Holdingstrings 316 connect the distal region of the pressurizing cannula 300 toan inflation seal 317 which comprises a continuous ring of preferablythin tubing attached to filter mesh 318 on its outer side. Filter mesh318 is bonded at its distal end around the circumference of bloodcannula 350, preferably at a cross-sectional position which closelyabuts rib 351.

[0152] Inflation seal 317 may be constructed from elastomeric ornon-elastomeric tubular material which encloses donut-shaped chamber319. When deployed, the inflation seal will expand to a diameter whichfits tightly against the lumen of aorta 399. The inflation seal willthus be capable of expansion to an outer diameter of at least 2 cm, morepreferably at least 2.5 cm, more preferably at least 3 cm, morepreferably at least 3.5 cm, more preferably at least 4 cm, morepreferably at least 4.5 cm. These diameter ranges will accommodate bothpediatric use and adult use. The inflation seal is typically acontinuous ring of very thin tubing attached to the mesh filter on oneside and to the pressurizing cannula by holding strings on the otherside.

[0153] The inflation seal should be able to maintain an internalpressure in chamber 319, without bursting, of greater than 55 mm Hg,more preferably greater than 60 mm Hg, more preferably greater than 70mm Hg, more preferably greater than 80 mm Hg, more preferably greaterthan 90 mm Hg, more preferably greater than 100 mm Hg, more preferablygreater than 110 mm Hg, more preferably greater than 120 mm Hg, morepreferably greater than 130 mm Hg, more preferably greater than 140 mmHg, more preferably greater than 150 mm Hg. The internal pressure neededwill depend on the pressure maintained in the aorta against the mesh.Thus, if the aortic pressure is 55 mm Hg, then the pressure in theinflation seal must be greater than 55 mm Hg to prevent leakage aroundthe seal. Typically, the aortic pressure will be at least 75 mm Hgbecause this level of pressure is needed to ensure adequate brainperfusion. It will be recognized that such inflation seal pressures aremuch higher than the maximum level that can be used in the pulmonaryvenous system because the veins and arteries therein will typically holdno more than about 40-50 mm Hg, or at most 60 mm Hg without rupture.

[0154] Chamber 319 is in fluid communication with a first tubularpassage 320 and a second tubular passage 321 which permit chamber 319 tobe inflated with gas, or preferably a fluid such as saline. Passage 320is in fluid communication with second lumen 312 of pressurizing cannula300, while passage 321 is in fluid communication with third lumen 314 ofpressurizing cannula 300. Passage 320 and 321 thereby interconnectchamber 319 with the second and third lumens 312 and 314, respectively,of pressurizing cannula 300.

[0155] In certain embodiments, inflation seal 317 will include a septum322 which blocks the movement of fluid in one direction around chamber319. If septum 322 is positioned in close proximity to the fluid entryport, then the injection of fluid will push all gas in chamber 319around inflation seal 317 and out through passage 321. In oneembodiment, the entry port and the exit port are positioned in closeproximity with septum 322 disposed between the entry and exit port. Inthis case, injection of fluid will force virtually all gas out ofinflation seal 317.

[0156] Filter mesh 318 is bonded at its proximal end to inflation seal317 and at its distal end to blood cannula 350, optionally at theproximal or distal edge of rib 351. Mesh 318 can be made of a materialwhich is reinforced or non-reinforced. Mesh 318, when expanded as shownin FIG. 7, may assume a substantially conical shape with a truncateddistal region. The mesh should be formed of a material having a poresize which obstructs objects 5 mm in size or less, more preferably 3 mmin size, more preferably less than 3 mm, more preferably less than 2.75mm, more preferably less than 2.5 mm, more preferably less than 2.25 mm,more preferably less than 2 mm, more preferably less than 1.5 mm, morepreferably less than 1 mm, more preferably less than 0.75 mm, morepreferably less than 0.5 mm, more preferably less than 0.25 mm, morepreferably less than 0.1 mm, more preferably less than 0.075 mm, morepreferably less than 0.05 mm, more preferably less than 0.025 mm, morepreferably 0.02 mm, and down to sizes just larger than a red blood cell.It will be understood that for a given pore size that blocks particlesof a certain size as stated above, that pore size will block allparticles larger than that size as well. It should also be understoodthat the necessary pore size is a function of blood throughput, surfacearea of the mesh, and the pressure on the proximal and distal side ofthe mesh. For example, if a throughput of 5-6 L/min. is desired at across-section of the aorta having a diameter of 40 mm, and a pressure of120 mm Hg will be applied to the proximal side of the mesh to obtain adistal pressure of 80 mm Hg, then a pore size of about □50 □m is needed.By contrast, in the pulmonary artery the same throughput is needed, butthe artery cross-section has a diameter of only 30 mm. Moreover, theproximal pressure is typically 40-60 mm Hg, while the distal pressure isabout 20 mm Hg. Thus, a much larger pore size is needed to maintainblood flow. If pore sizes as disclosed herein for the aorta were used inthe pulmonary artery, the blood throughput would be insufficient tomaintain blood oxygenation, and the patient would suffer rightventricular overload because of pulmonary artery hypertension.

[0157] It will also be understood for this cannula apparatus that bloodflow to the patient is maintained by blood passage through blood cannula350, and not through mesh 318. Thus, the cannula must have an innerdiameter which allows blood throughput at a mean flow rate of at least3.0 L/min., more preferably 3.5 L/min., more preferably 4 L/min., morepreferably at least 4.5 L/min., more preferably at least 5 L/min., andmore. Of course, flow rate can vary intermittently down to as low as 0.5L/min. Therefore, the inner diameter of blood supply cannula 350 willtypically be at least 9 F (3.0 mm), more preferably 10 F, morepreferably 11 F, more preferably 12 F (4 mm), more preferably 13 F, morepreferably 14 F, more preferably 15 F (5 mm), and greater. Depending onthe inner diameter and thickness of the tubing, the outer diameter ofblood cannula 350 is approximately 8 mm. Meanwhile, the pressurizingcannula 300 and handle at the collar region 383 have outer diameters ofapproximately 10.5 mm and 13.0 mm, respectively. The foregoing rangesare intended only to illustrate typical device parameters anddimensions, and the actual parameters may obviously vary outside thestated ranges and numbers without departing from the basic principlesdisclosed herein.

[0158] In use, the cannula with associated filter has syringe 307 whichis removed, and aseptically filled with a saline solution. The syringeis then attached to pressurizing cannula 300, and cap 306 is removed.Saline is injected until saline exits from luer 304, thereby purgingsubstantially all gas from the inflation seal and dual lumen system ofpressurizing cannula 300. Cap 306 is then replaced and secured to thepressurizing cannula 300.

[0159] Cardiac surgery can then be conducted in accordance withprocedures which employ standard cannula insertion, as known in the art,and discussed more fully herein. The mesh 318 and inflation seal 317 areenclosed under handle 380 at the enlarged end, just beyond the distaltip of pressurizing cannula 300. The cannula is introduced into theaorta, preferably the ascending aorta, of a patient through an incision,and the incision may be tightened about the cannula by use of a “pursestring” suture. Cardiopulmonary bypass occurs through blood cannula 350.

[0160] With the cannula in place, the filter is ready for deployment.The surgeon grips the handle, and the blood cannula 350 and pressurizingcannula 300 are pushed forward. This movement breaks the seal at the tipof the handle and allows the blood cannula and pressurizing cannula tothrust forward, thereby releasing the filter. The plunger of the syringeis then depressed within the barrel to expand the inflation seal. Theinflation seal expands to ensure contact with the inside of the aorta atall points along the circumference of the lumen. The syringe is thenlocked in place to prevent inflation or depressurization of theinflation seal during use.

[0161] The aorta is then cross-lamped at a region between the heart andthe cannula incision. Embolic material dislodged from the aorta iscaught and trapped by filter mesh 318. The bypass-oxygenator system isthen started to achieve cardiopulmonary bypass through blood cannula350. Cardiac surgery is then performed while the filter and inflationseal are maintained in place for a number of hours, typically 8 hours orless, more typically 7 hours or less, more typically 6 hours or less,more typically 5 hours or less, more typically 4 hours or less, moretypically 3 hours or less, and more typically 2 hours or less.

[0162] At the end of the cardiac surgery, the filter is depressurizedand removed from the ascending aorta. The syringe lock is released and,while holding handle 380, the pressurizing cannula is drawn back. Thiswill cause release of saline from inflation seal 317, and will retrievethe filter mesh, inflation seal, and pressurizing cannula back into andunder the handle, as it was configured before deployment. Notably,embolic material collected in the filter is also trapped under thehandle at its enlarged segment. Optionally, the inflation seal may bedeflated before pull-back of the pressurizing cannula by operating thesyringe to withdraw saline from the inflation seal. Once the associatedfilter has been retrieved under the handle, the cannula can be removedfrom the patient without damaging the aortic incision by using standardprocedures.

[0163] In another embodiment, a cannula is provided as depicted in FIGS.6 and 7 with a continuous filter mesh as shown in FIG. 4 which extendsbeyond and over the lumen of the blood cannula so that blood from thecannula passes through the mesh before circulating within the patient.With reference to FIG. 9, the device may include a pressurizing cannula300, blood cannula 350, inflation seal 317 and mesh 318. The device mayoptionally include a handle 380 and an inflation system as describedabove with reference to FIGS. 6 and 7. Moreover, the inflation systemmay be carried by either the pressurizing cannula or the blood cannula.In certain embodiments, the blood cannula and pressurizing cannula willbe integrally combined into a single unitary component, and theinflation system may be carried either within or on the outside of theblood cannula. It will be understood that FIG. 9 shares many features incommon with FIGS. 6 and 7, and the numbering of apparatus components hasbeen duplicated so that appropriate description can be found withreference to FIGS. 6 and 7.

[0164] In another embodiment, a cannula is provided with an inflatableloading balloon as depicted in FIG. 10. The device includes cannula 421having pressurizing lumen 422 which extends from the proximal to thedistal end. The cannula is equipped with an inflatable loading balloon423 which, when inflated, exerts a radial outward force on stiffeningwire ribs 424. The ribs support filtration mesh 425 which extends fromthe surface of the cannula at one edge to inflation seal 426 at anotheredge. A plurality of retrieving strings 427 are optionally providedwhich are attached at another end (not shown) to the plunger of thepressurizing syringe and therefore can be activated (advanced andwithdrawn) by the motion of the pressurizing syringe which operates atthe proximal end of cannula 421. Alternatively, the strings may beattached at the proximal end to a ring or slide which can be drawn topull back, or advanced to let out the strings. FIG. 10A shows across-sectional view of aorta 399 taken through section line I-I. It canbe seen that the cannula is equipped with a plurality of stiffening wireribs 424 which extend radially outward when loading balloon 423 isexpanded.

[0165] In another embodiment, a cannula with associated filter anddistal flow diffuser is provided in FIGS. 11 and 11a. With reference toFIGS. 11 and 11a, the device includes a pressurizing cannula 300, bloodsupply cannula 350 and a blood filtration assembly 315 comprisingholding strings 316 inflation seal 317, filter mesh 318, chamber 319,tubular passages 320 and 321, and septum 322. As shown in FIG. 11 a thedistal end of the blood supply cannula is closed with a cap 390 and theflow diffuser 395 is a rounded, hemispherical shape to facilitate theinsertion of the distal end of the cannula 350 into the vessel. The flowdiffuser 395 tapers towards the proximal end of the cannula 350 startingfrom the cap 390. The shape of the diffuser is preferably conical, inorder to avoid damaging the blood. However, other shapes, includingpyramidal shapes, may be employed.

[0166] In this FIGS. 11 and 11a embodiment, a plurality of outletopenings 391 are formed in the sidewall of the cannula 350 adjacent toits distal end. The openings may have an arched configuration, with thecurved portion 392 of each arch oriented in the upstream direction.Although any number of openings are possible, a preferred embodiment hassix openings. Preferably the total area of the openings is greater thanthe area of the distal end opening of a conventional catheter of thesame diameter. The length of the openings 391 are also preferablygreater than the length of the flow diffuser 395.

[0167] In another embodiment, a cannula with associated filter and flowdiffuser is provided as depicted in FIGS. 12 and 12a. In thisembodiment, the distal end of the cannula 350 contains a diffuser 396with a helical configuration. The diffuser 396 can be held in placewithin the cannula by the tapering configuration of the distal end ofthe cannula, by adhesives, by ultrasonic welding, or by some othersuitable means. The diffuser is preferably formed from a flatrectangular member with a single one-hundred-eighty degree twist. Inthis embodiment, the distal end of the cannula is partially blocked.Additionally, any number of outlet openings 397 may be formed in thesidewall of the cannula.

[0168] The intra-cannula flow diffusers of FIG. 11 and FIG. 12 may alsobe employed proximal to the filter by, for example, positioning thediffuser within the blood cannula of the device depicted in FIG. 9.Other variations and details of intra-lumen flow diffusers may be foundin Cosgrove et. al., Low Velocity Aortic Cannula, U.S. Pat. No.5,354,288, which is incorporated by reference herein.

[0169] In another embodiment, a blood cannula with associated filter andflow diffuser is provided as in FIG. 13. In this embodiment the proximalend of a flow diffuser 702 is connected to the distal end of the cannula350 by a plurality of structural supports 704. The diffuser 702 ispreferably conical, although other shapes may be used. The distal end ofthe flow diffuser 702 extends to the apex of the filter 706 by virtue ofa linear shaft 708 said shaft running through the center of the expandedfilter. In this embodiment the flow diffuser 702 diffuses blood flowproximal to the filter 706.

[0170] In another embodiment, an arterial blood cannula is provided asin FIG. 14. In this embodiment the flow diffuser 802 is contained withinthe distal end of the blood cannula 10. In a preferred embodiment, thediffuser 802 is the helical diffuser shown in FIG. 12 and 12 a. The flowdiffuser 802 can be held in place by the tapering configuration of thedistal end of the cannula, by adhesives, by ultrasonic welding, or byany other suitable means. Unlike the diffuser of FIG. 12, the distal endof the diffuser 802 is attached to the apex of the filter 806 by virtueof a linear shaft 808 said shaft running through the center of theexpanded filter. The shaft may be any shape which will not traumatizeblood components, and preferably comprises a rounded surface whichtapers outward in the distal direction. In this embodiment the flowdiffuser also diffuses cannula blood flow proximal to the filter. Thecannula 350 optionally contains openings 803 in its distal end 804 tofurther diffuse the cannula blood. In an alternate embodiment, blooddiffuser 802 is contained within cannula 350 but is not connected tofilter 806 said filter being supported as disclosed in FIG. 9.

[0171] It is to be understood that flow diffusers such as those of FIG.11-14 can be used in any blood filter device having a blood supplycannula and associated filter, including the devices depicted in FIG. 2and FIG. 3. Furthermore, the diffuser of FIG. 14 may be employed insidea cannula having a distal filter, such as in FIG. 7, thus creating ablood filter device with two filters, one proximal to and one distal tothe cannula opening.

[0172] In an alternative embodiment, shown in FIG. 15, a blood filterdevice and associated filter 906 include a generally cylindrical filtersleeve 908 disposed circumferentially about the distal end of cannula10, and attached to four control lines 902 a, 902 b, 904 a, and 904 b.Proximal force on unroll control lines 904 a and 904 b unrolls filtersleeve 908 from its depicted position so as to capture the filter asshown in FIG. 16. In this embodiment, the manner of unrolling the filtersleeve is analogous to the unrolling of a latex condom. Although thesleeve may be any shape, provided it both encases the device and rollsup in response to the control lines, in a preferred embodiment thesleeve has a circular cross-section.

[0173] In FIG. 15 the filter sleeve 908 is rolled back distal to thefurther to allow the filter to be fully expanded. FIG. 15 shows across-sectional cut-away of the sleeve. The full sleeve, not depicted,is a continuous piece surrounding the cannula about a 360 degree axis.In a preferred embodiment, a circular condom-like sleeve is attached atthe outer-diameter of the cannula along the arc of circle 910. Thecondom-like sleeve has a distal opening to permit exit of the cannulatip. In a preferred embodiment a pair of control lines 902 a and 904 aenter a control lumen at points 928 and 929 respectively and run insidecontrol lumen 922 adjacent the cannula lumen until exiting the controllumen at a proximal point on the cannula (not shown). In the preferredembodiment, control lines 902 b and 904 b similarly enter and exit asecond control lumen 924 at points 926 and 927 respectively, said pointslocated 180 degrees from the first lumen on the cannula's outerdiameter.

[0174] As shown in FIG. 16, unroll control lines 904 a and 904 b areattached to sleeve 908 at points 914 and 916 respectively, said pointslocated at the proximal end of the sleeve. Consequently, when sleeve 908is rolled-up, as shown in FIG. 15, points 914 and 916 are rolled intothe center of the nautilus-shaped lip of sleeve 908 while unroll controllines 904 a and 904 b are rolled-up along side the sleeve.

[0175] In contrast, roll-up control lines 902 a and 902 b are attachedto the cannula at points 918 and 920 respectively. Points 918 and 920are located on arc 910. When the sleeve is rolled-up as shown in FIG. 15the roll-up control lines 902 a and 902 b run from their respectivepoints of attachment 918 and 920, along the exposed side of therolled-up sleeve, and enter the control lumens 922 and 924 at points 926and 928 respectively. After entering the control lumens, the roll-uplines proceed through the control lumens until exiting at points (notshown) proximally located on the cannula.

[0176]FIG. 16 shows the same blood filter device with blood cannula andassociated filter as FIG. 15 but with the sleeve 908 fully unrolled andcapturing filter 906. The unrolled sleeve provides a compact, smoothprofile for the device's introduction to and retraction from a vessel.In order to unroll the sleeve from the FIG. 15 position the unroll lines904 a and 904 b of FIG. 16 are pulled in a proximal direction, away fromthe cannula tip. Consequently, points 914 and 916 are positioned at theproximal end of unrolled sleeve 908.

[0177] When the sleeve is in the unrolled state, the roll-up controllines 902 a and 902 b run from points 918 and 920 respectively, alongthe underside of the sleeve 908, around the proximal end of the sleeve,and then distally along the outer side of the sleeve before entering thecontrol lumens 922 and 924 at points 926 and 928 respectively. Afterentering at points 926 and 928, the roll-up control lines 902 a and 902b travel through the control lumens until exiting the control lumens atpoints (not shown) located at the proximal region of the cannula. Whenthe sleeve is in the unrolled position as shown in FIG. 16, the roll-uplines may be pulled in a proximal direction, away from the cannula tip.Pulling the roll-up lines causes the sleeve 908 to roll-up untilreaching the rolled-up state shown in FIG. 15. In a preferred method ofuse, the sleeve 908 is unrolled prior to insertion of the cannula in avessel, rolled up during mesh deployment, and once again unrolled priorto cannula retraction.

[0178]FIG. 17 shows a cross-sectional detail of the sleeve 908 in theunrolled state, with emphasis on the points of attachment for thecontrol lines. In the FIG. 17 embodiment, the sleeve, which is acontinuous about 360 degrees (not shown), is directly connected to thetwo roll-up lines 902 a and 902 b at points 918 and 920 respectively.Alternatively, the roll-up lines are attached directly to the cannula atpoints neighboring 918 and 920 located immediately under the distal endof the sleeve. Pulling the roll-up lines in a proximal direction, asshown by the arrows in FIG. 17, causes the sleeve to roll-up like acondom. Accordingly, the sleeve material should be thin enough to avoidbunching and to provide smooth rolling in reaction to proximal forceexerted by the roll-up lines. In a preferred embodiment, the sleeve ismade of latex, with a thickness of between 3 and 14 thousandths of aninch. In a more preferred embodiment, the sleeve is made of latex with athickness of between 4 and 16 thousandths of an inch. The invention mayalso use silicone or another silastic, biocompatible material toconstruct the sleeve. Other materials as are known in the art may permituse of a sleeve with a thickness of less than 6 thousandths of an inchprovided the material gives suitable assurances against breaking ortearing.

[0179]FIG. 18 is a three-dimensional depiction of the cannula 350,filter 906 and sleeve 908, with sleeve 908 in the rolled-up state. Inone embodiment, the filter 906 is located distal to the cannula openingsuch that cannula output is filtered upon exiting the cannula. Inanother embodiment the filter is located proximal to the cannula openingsuch that cannula output is downstream of the filter. The cannulaopening may optionally have a planar diffuser 932. Filter 906 is made ofa mesh which is contiguous with a sealing skirt 930. With the exceptionof entrance point 933 both the roll-up and unroll lines enter and exitthe cannula at points not shown. In a preferred embodiment, the controllines attach to a control line actuating mechanism such as a capstan,ring or pulley (also not shown). In this embodiment, the structureadapted to open and close the filter may be an umbrella frame (notshown), such as depicted in FIG. 1, or alternatively an inflationballoon (not shown), such as shown in FIG. 7 and FIG. 9. The FIG. 18embodiment may be used with any of the various means to actuate thestructure as described herein.

[0180] Pulling unroll control lines 904 a and 904 b in a proximaldirection causes the capture sleeve to roll out over the top of thefilter. Subsequently pulling the roll-up control lines 902 a and 902 bin a proximal direction rolls-up the capture sleeve thereby permittingfilter deployment. In FIG. 18, the unroll lines are oriented at an angleof 180 degrees from one another along the circumference of the filter(thus 904 b not shown). The roll-up lines 902 a and 902 b are similarlyoriented at an angle of 180 degrees from one another. However, as withthe inventions of FIG. 15-17, this embodiment may employ any number ofcontrol lines spaced at varying differences around the outer diameter ofthe filter sleeve.

[0181]FIG. 19 shows an alternative embodiment wherein one control ring936 controls rolling and unrolling of the sleeve 934 with the assistanceof a pulley mechanism. The control ring 936 is movable in both theproximal and distal directions along the outer diameter of the cannula(not shown). Control ring 936 is directly attached to unroll controllines 904 a and 904 b and attached to roll-up control lines 902 a and902 b through pulley 934. Proximal movement of the control ring causesthe sleeve 908 to unroll. Distal movement conversely causes sleeve 908to roll up.

[0182] In another embodiment of the blood filtration device, as shown inFIG. 20, the cannula 350 contains a collapsible or deformable section938 such that the cannula can accommodate the filter 906 and filter seal907, as well as other filter components. The collapsible section 938 ismade out of an elastomeric material such as latex or silicone. Inanother embodiment the collapsible section is a double walled balloon.In a preferred embodiment the section is made of a flexible materialwith built in memory such that the collapsible walls automaticallyreturn to their non-collapsed state when deployment force expands thefilter means. The collapsing section begins proximal to the filter seal907 when the filter is in its collapsed state. In the embodiment shown,the collapsing section 938 begins just proximal to the site of thefilter seal 907 and has a length equal to the length of the filter andfilter seal. In an alternative embodiment, the collapsing sectionextends to the tip of the catheter from just proximal to the filterseal. The deformable section collapses radially inward when thefiltration assembly is closed in order to produce a low-profile distalend to the cannula. Thus, a portion of the radial volume of the cannulais occupied by the filtration assembly when the filtration assembly isdeployed; however, the blood flowing through the cannula subsequentlyblows the deformable cannula walls outwards to allow the flow of bloodthrough the entire cannula diameter.

[0183] In another embodiment of a blood filtration device, shown inFIGS. 21 and 22, the cannula 350 is composed of a medically acceptableelastic material, such as latex, silicone, rubber, and the like. Asshown in FIG. 22, the cannula has an intrinsic length and diameter whichcharacterizes the cannula when it is not under axial stress. Theintrinsic length and diameter of the cannula vary according to vesselsize. The cannula may be closed ended with a cap diffuser of the typedisclosed in FIG. 11. Alternatively, the cannula may be partially closedat the tip as in FIG. 12.

[0184] As shown in FIG. 21, a stylet 944 is placed in the cannula 350and engages the cannula tip. In an alternative embodiment, the styletengages a ring suspended at the opening of an open tip. When insertedfully into the cannula, the lengthy stylet 944 engages the distal tip ofthe cannula and axially stretches the cannula body as shown. In this waythe cannula is stretched so as to reduce cannula diameter. A finger grip946 secured to the proximal end of the stylet includes latch member 948.The latch member engages a recess 950, formed on a proximal fitting 952of the cannula, in order to maintain the cannula's stretchedconfiguration. After insertion in the vessel, the elastic cannula isradially expanded and shortened by depressing latch member 948 andwithdrawing the stylet as in FIG. 22.

[0185] In this embodiment, filter 908 is fixed to the outer diameter ofthe unexpanded elastic cannula 350 by tether lines 954 and 956 such thatwhen the stylet is introduced cannula extension causes the tether linesto go taut. This in turn causes the filter to contour to the cannula.Conversely, as shown in FIG. 22, when the stylet is removed the cannulashortens thereby permitting expansion of the filter. Although variousbiasing and filter opening mechanisms may be used, in a preferredembodiment, the filter itself is made of memory-wire biased to an openstate.

[0186] In another embodiment shown in FIGS. 23 and 24, the distalcannula portion 960 upon which the filter assembly 962 is mounted is, atleast in part, a radially flexible material or composite constructionwhich is normally in a necked down, contracted position. This allows thecontracted filter assembly 962 to create as small of a profile aspossible for insertion into the blood vessel. The necked-down portion964 of the distal cannula is opened by inserting a close fittingexpander 966 through the necked-down portion. The expander 966 has adistal end 967. As a result of the expander insertion, the filterassembly 962 exhibits an extruding profile relative to the outercontours of the distal cannula. Optionally as shown in FIG. 24, thefilter assembly 962 may be fully deployed by a deployment mechanism (notshown), as previously described herein. In both FIGS. 23 and 24, theexpander is fixed relative to the proximal cannula 968. Both are moveddistally relative to the distal cannula so as to insert the expanderinto the collapsible section. Alternatively, the expander 966 may moveindependent of the proximal cannula 968.

[0187] In another embodiment shown is FIGS. 25 and 25A to 25D, cannula350 includes filter 906 having skirt 970 disposed around its outermostedge. Skirt 970 is an elasticmeric strip of material (e.g., silicon orother suitable material) attached to the proximal edge of the filtermesh. Skirt 970 forms a compliant edge which conforms to vessel lumentopography and gives a better seal with the vessel lumen when the filteris deployed. Moreover, the compliant edge 970 allow for changes in thevessel interior dimension as the vessel pulses from systole to diastole.Both unroll control lines 904 a and 904 b, as well as roll-up controllines 902 a and 902 b (not shown) are routed through tube 978 and thenthrough the cannula housing at location 971 and thereafter ride withintubing 972 to the point where they are manipulated outside of the body.In addition to the roll-up and unroll control lines, a fifth controlline is also carried through tube 972 and location 971 for the purposeof operating the umbrella frame 973 depicted in FIG. 25. This controlline can ride either inside or outside of tube 978. The umbrella frameconsists of a series of primary struts 974 extending from the distal toproximal end of the mesh and disposed circumferentially thereabout, anda series of secondary struts 975. Struts 975 connect at their proximalend to struts 974 and at their distal end are slideably connected to theaxis of the conical filtration mesh. Secondary struts 975 thereforeoperate to open and close the expansion frame between a radiallyexpanded and radially contracted condition.

[0188] In another embodiment shown in FIG. 26, cannula 350 includes onits distal end a “windsock” or open-ended sleeve 976 which is either aporous mesh, a non-porous material (e.g., silicon), or a non-porousmaterial with holes which allow some degree of lateral blood flow. InFIG. 26, the windsock cannula is shown deployed within aorta 99. As canbe seen, embolic debris dislodged upstream of the cannula will becarried through the windsock 976 and will exit the distal opening 977.Sleeve 976 thereby prevents passage of embolic material laterally in theregion of the carotid arteries and thereby prevents or reduces theoccurrence of embolic material reaching the brain. At the same time,however, the windsock apparatus overcomes difficulties associated withfilter blockage due to blood clotting and buildup of debris bydelivering a high volume of blood downstream of the carotid arterieswithout the need to pass laterally through the sleeve.

[0189] In another embodiment, a filter is provided in the form of a“lobster trap” as depicted in Reger et al., U.S. Pat. No. 5,108,419(FIGS. 2, 14, 15) and U.S. Pat. No. 5,160,342, incorporated herein byreference. A filter of this construction allows debris into anentrapment chamber through a small opening. A series of other smallopenings generally are included within this structure, and debristherefore advances one-way, distally through the structure. However,once the material enters the structure it cannot get out, and thus, ifthere is a momentary reversal of blood flow within the vessel, embolicdebris cannot wash away from the filter.

[0190] It is to be understood that the blood filtration devices of FIG.15-FIG. 26, as well as the lobster trap, may optionally employ anyelongated insertion member in place of blood cannula 350. The elongatedinsertion member need not contain a lumen.

[0191] As a purely illustrative example of one of the methods offiltering blood as disclosed herein, the method will be described in thecontext of cardiac bypass surgery as described in Manual of CardiacSurgery, d. Ed., by Bradley J. Harlan, Albert Spar, Frederick Harwin,which is incorporated herein by reference in its entirety.

[0192] A preferred method of the present invention may be used toprotect a patient from embolization during cardiac surgery, particularlycardiac bypass surgery. This method includes the following steps:introducing a mesh into an aorta of the patient; positioning the mesh tocover substantially all of the cross-sectional area of the aortapreferably proximal to the carotid arteries so that the mesh may entrapembolic matter or foreign matter in the blood before it can escape tothe brain; adjusting the mesh to maintain its position coveringsubstantially all of the cross-sectional area of the aorta; and removingthe mesh and the entrapped foreign matter from the aorta. A variantcomprises placing a cylindric mesh at the level of the take off of thecerebral vessel to divert emboli otherwise destined for the brain toother parts of the body.

[0193] During the cardiac surgery, the aorta is clamped a number oftimes. Because clamping the aorta dislodges atheromatous material fromthe walls of the aorta, which is released into the bloodstream, the meshmust be positioned within the aorta before clamping begins. Atheromatousmaterial also accumulates behind the clamps during the surgery and,because removal of the clamps releases this material into thebloodstream, the mesh must be maintained within the blood stream forabout four to ten minutes after removal of the clamps. Because the aortais often a source of much of the atheromatous material that iseventually released into the bloodstream, it is preferable to place themesh in the aorta between the heart and the carotid arteries. Thisplacement ensures that foreign matter will be entrapped before it canreach the brain.

[0194] For illustration purposes, the method for filtering blood will bedescribed in connection with the device depicted in FIG. 4. After apatient has been anaesthetized and the patient's chest has been openedin preparation for the bypass surgery, the cannula 205, ranging fromabout 22 to about 25 Fr.O.D. in size, is introduced into an incisionmade in the aorta. The cannula 205 is sutured to the aortic wall, andthe heart is paralyzed. The device 10 is stored in a closed positionwithin the cannula 205, in which the balloon 230 is deflated and foldedin upon itself, and the mesh 220 is closed. The cannula 205 and thedevice 10 will not interfere with other equipment used in the surgicalprocedure.

[0195] The blood filter device 10 is then inserted into the aortathrough the cannula 205 via the tie lines 250. Saline is introduced intothe balloon 230 through the actuation assembly 260 from anextracorporeal reservoir, and the device 10 gradually assumes an openposition in which the balloon 230 is inflated in a donut-shape and themesh 220 is opened to cover substantially all of the cross-sectionalarea of the vessel. In the opened position, the device 10 is ready toentrap foreign matter in the blood flow. By adjusting the amount ofsaline introduced into the balloon 230, the surgeon may control theamount of inflation and consequently the degree to which the mesh 220 isopened. After the device 10 has been actuated, blood from a bypassmachine is introduced into the aorta through the cannula 205 and isfiltered by the device 10.

[0196] To block the flow of blood back into the heart, the surgeoncross-clamps the aorta, or, in an alternative procedure, balloonoccludes the artery or aorta. Cross-clamping and/or balloon occludingthe aorta dislodges atheromatous material from the walls of the aortaand releases it into the blood flow. Because cross-clamping is doneupstream from the device 10, the atheromatous material will be filteredfrom the blood by the device 10. While the aorta is cross-clamped, thesurgeon grafts one end of a vein removed from the patient's leg on tothe coronary artery. After the surgeon checks the blood flow to makesure there is no leakage, the aortic clamps are removed. Atheromatousmaterial accumulates behind the clamps and, when the clamps are removed,this material is released into the blood flow, which will be filtered bythe device 10. The flow rate from the bypass machine is kept low tominimize embolization, and the heart is made to beat again.

[0197] During surgery, the position of the mesh may require adjustmentto maintain its coverage of substantially all of the cross-sectionalarea of the aorta. To accomplish this, the surgeon occasionally palpatesthe outside of the aorta gently in order to adjust the device 10 so thatthe mesh 220 covers substantially all of the cross-sectional area of theaorta. The surgeon may also adjust the location of the device 10 withinthe aorta.

[0198] The device 10 may also be used in conjunction with TCDvisualization techniques. Through this technique, the surgeon mayactuate the device 10 only when the surgeon expects a flurry of embolisuch as during aortic cannulation, inception, and termination of bypass,aortic clamping, and clamp release.

[0199] The surgeon then clamps the aorta longitudinally to partiallyclose the aorta, again releasing the atheromatous material to befiltered by the device 10. Holes are punched into the closed off portionof the aorta, and the other end of the vein graft is sewn onto the aortawhere the holes have been punched. The aortic clamps are then removed,again releasing accumulated atheromatous material to be filtered fromthe blood by the device 10. The surgeon checks the blood flow to makesure there is no leakage. The heart resumes all the pumping, and thebypass machine is turned off, marking the end of the procedure.

[0200] The saline is then removed from the balloon 230 via the actuationassembly 260, deflating the balloon 230 and closing the mesh 220 aroundthe entrapped emboli. The device 10 is then retracted into the cannula205 by pulling the tie lines 250 into the cannula 205. If the balloon230 has not been deflated sufficiently before retraction, excess salinemay be squeezed out of the balloon 230 as it is retracted into thecannula 205. Finally, the cannula 205 and the device 10, along with theentrapped emboli, are removed from the body. Because the device 10 is inplace throughout the procedure, any material released during theprocedure will be entrapped by the device 10.

[0201] When the device 10 is used in conjunction with other invasiveprocedures, the dimensions of the device should be adjusted to fit thevessel affected. An appropriate mesh also should be chosen for bloodflow in that vessel. In use, the device may be positioned so that it isplaced downstream of the portion of the vessel that is affected duringthe procedure, by clamping or other step in the procedure. For example,in order to entrap emboli material in a leg artery, the cone-shapedfilter can be placed such that the cone points toward the foot.

[0202] An advantage of the devices and methods of the present inventionand the methods for filtering blood described herein is that it ispossible to entrap foreign matter resulting from the incisions throughwhich the devices are inserted. Another advantage of the devices of thepresent invention is that the flexibility of the inflatable balloonallows it to conform to possible irregularities in the wall of a vessel.

[0203] In other methods of the invention, the filter is decoupled fromthe cannula and the filter is disposed on an elongate member separatefrom the cannula. As such, while the cannula is inserted into the aortagenerally upstream of the aortic arch, the filter disposed on anelongate member may or may not be entered through the same incision asthe cannula. Thus, the filter may enter by any of the following routes;(1) through the cannula and deployed downstream of the cannula, (2)through the cannula and deployed upstream of the cannula, (3) throughthe left subclavian artery and deployed at a point either upstream ordownstream of the cannula, and (4) through the femoral artery andthereafter into the aortic arch and deployed either upstream ordownstream of the cannula. In other methods of the invention, the filteris deployed during stages of the cardiac surgery procedure and removedbetween certain stages.

[0204] The cerebral embolic signals during coronary artery bypassgrafting are as follows (expressed as percentage embolic release perevent): cannula on=2%, bypass on=6%, aortic cross clamp on=6%, aorticcross clamp off=21%, partial occlusion clamp on=7%, partial occlusionoff=14%, bypass off=8%. Moreover, during the approximately 5.8 minuteinterval between bypass on and aortic cross clamp on, approximately 4%of embolic material is released. During the approximately intervalbetween placement of the cross clamp and removal of the aortic crossclamp, a time of approximately 38.8 minutes, about 13% of the embolicmaterial is released. During the approximately 4.1 minute intervalbetween removal of the aortic cross clamp and installation of thepartial occlusion clamp, approximately 9% of embolic material isreleased. During the approximately 9.7 minute interval between placementof the partial occlusion clamp and removal of the partial occlusionclamp, approximately 2% of embolic material is released. Finally, duringthe 7.3 minute interval between removal of the partial occlusion clampand turning bypass off, approximately 8% of embolic material isreleased.

[0205] Thus, in one embodiment, it is desirable to have a filter deployshortly before cross clamp removal and removed shortly thereafter. Inanother embodiment, it is desirable to have a filter deploy only duringthe period just after cross clamp placement and removed after crossclamp removal. In still another embodiment, it is desirable to have thefilter deployed just before placement of the aortic cross clamp andmaintained until after removal of the aortic cross clamp. Alternatively,the filter may be deployed before and removed after installation of thecross clamp or removal of the cross clamp or placement of the partialocclusion clamp or removal of the partial occlusion clamp. In stillanother embodiment, the filter is deployed only during the intervalbetween placement and removal of the aortic cross clamp. Thus, in someembodiments it will be desirable to have the filter deployed onlytransiently for events of short duration, e.g., cannula on, bypass on,cross clamp on, cross clamp off, partial occlusion clamp on, partialocclusion clamp off, and bypass off. In other embodiments, it will bedesirable to have the filter deployed throughout a number of thesemanipulative events. In still other embodiments it will be desirable tohave the filter deployed only during one. or more interval between thesemanipulative events. For a discussion of embolic staging during bypasssurgery the reader is referred to Barbut et al., Stroke 25:2398-2402(1994), expressly incorporated herein by reference.

[0206] While particular devices and methods have been described forfiltering blood, once this description is known, it will be apparent tothose of ordinary skill in the art that other embodiments andalternative steps are also possible without departing from the spiritand scope of the invention. Moreover, it will be apparent that certainfeatures of each embodiment can be used in combination with devicesillustrated in other embodiments. For example, the inflation systemillustrated in FIG. 7 can be used with any of the devices depicted inFIGS. 1-4. Accordingly, the above description should be construed asillustrative, and not in a limiting sense, the scope of the inventionbeing defined by the following claims.

What is claimed is:
 1. A method for deploying a vascular filter deviceduring a procedure, comprising: (a) positioning a vascular filter devicein a vasculature of a patient distal of a portion of a blood vessel tobe accessed during a procedure, the filter device comprising; (i) aguide member comprising a proximal end and a distal end; (ii) means forfiltering coupled to said distal end of said guide member; (iii) meansfor deploying said means for filtering, said means for deploying beingcoupled to said guide member; and (iv) a restraining mechanism coupledto said guide member and said means for filtering, said restrainingmechanism being adapted to prevent said means for filtering beingdeployed, said restraining mechanism comprising: (1) a sleevesurrounding said distal end of said guide member, said sleeve having aclosed state and an open state; and (2) a securing member coupled tosaid sleeve and retaining said sleeve in a closed position; and (b)removing said securing member to release said sleeve to allow saidsleeve to move to said open state where said means for filtering isdeployed.
 2. A method as recited in claim 1, wherein said means forfiltering comprises a filter.
 3. A method as recited in claim 3, whereinsaid means for deploying comprises a plurality of struts coupled to saiddistal end of said guide member, at least one of said plurality ofstruts being biased to extend outwardly to deploy said filter.
 4. Amethod as recited in claim 3, further comprising releasing saidplurality of struts to said at least one of said plurality of saidstruts to extend outwardly to deploy said filter.
 5. A method as recitedin claim 1, further comprising positioning a capture catheter on atleast a portion of said guide member.
 6. A restraining mechanismconfigured to prevent a plurality of struts of a filter device fromextending outwardly prior to deploying a filter of the filter device,the restraining mechanism comprising: (a) a sleeve adapted to bedisposed substantially at a distal end of the filter device, said sleevebeing adapted to apply a restraining force to the plurality of struts ofthe filter device to prevent the plurality of struts from extendingoutwardly; and (b) at least one actuating member coupled to said sleeve,said at least one actuating member being adapted to release saidrestraining force of said sleeve and enable the plurality of struts ofthe filter device to extend outwardly.
 7. A restraining mechanism asrecited in claim 6, wherein said at least one actuating member isadapted to cause said sleeve to move in a proximal direction upon movingsaid at least one actuating member in said proximal direction.
 8. Arestraining mechanism as recited in claim 6, wherein said sleeve iscoupled to at least two of said plurality of struts.
 9. A restrainingmechanism as recited in claim 6, wherein said sleeve comprises at leastone preferential separation region.
 10. A restraining mechanism asrecited in claim 9, wherein said at least one actuating membercooperates with said at least one preferential separation region and isadapted to preferentially separate said sleeve at said at least onepreferential separation region.
 11. A restraining mechanism configuredto prevent a plurality of struts of a filter device from extendingoutwardly prior to deploying a filter of the filter device, therestraining mechanism comprising: (a) means for applying a restrainingforce to the plurality of struts of the filter device to prevent theplurality of struts from extending outwardly, said means for apply therestraining force being coupled to at least one of the plurality ofstruts; and (b) at least one actuating member cooperating with saidmeans for applying the restraining force, said at least one actuatingmember being adapted to release said restraining force of said means forapplying said restraining force and enable the plurality of struts ofthe filter device to extend outwardly to deploy the filter.
 12. Arestraining mechanism as recited in claim 11, wherein said means forapplying the restraining force comprises a sleeve attached to each ofsaid plurality of struts, said sleeve comprising at least onepreferential separation region.
 13. A restraining mechanism as recitedin claim 12, wherein said at least one actuating member cooperates withsaid at least one preferential separation region, said at least oneactuating member being adapted to cause said means for applying therestraining force to preferentially separate at said at least onepreferential separation region.
 14. A restraining mechanism as recitedin claim 11, wherein said means for applying the restraining forcecomprises a sleeve substantially surround the plurality of struts.
 15. Arestraining mechanism as recited in claim 14, wherein said sleeve isadapted to slide in a proximal direction upon moving said actuatingmember in the proximal direction.
 16. A restraining mechanism as recitedin claim 15, wherein said sleeve is a polymer sleeve.
 17. A method forreleasing a plurality of struts of a filter device during a procedure,comprising: (a) positioning a filter device in a vasculature of apatient distal of a portion of a blood vessel to be accessed during aprocedure, the filter device comprising: (i) a guide member comprising adistal end; (ii) a plurality of struts cooperating with said distal endof said guide member; (iii) a filter coupled to said guide member; and(iv) a restraining member cooperating with said plurality of struts toprevent said plurality of struts from extending outwardly; and (b)actuating an actuating member cooperating with said restraining member,wherein actuating said actuating member releases said plurality ofstruts to deploy said filter.
 18. The method as recited in claim 17,wherein actuating said actuating member comprises moving said actuatingmember in a proximal direction.
 19. The method as recited in claim 17,wherein actuating said actuating member further comprises moving saidactuating member in a proximal direction to remove said actuating memberfrom cooperating with said restraining member.
 20. A filter devicecomprising: (a) a guide member comprising a distal end, a proximal end,and a lumen extending from the distal end to the proximal end, (b) aplurality of struts coupled to said guide member, at least one of saidplurality of struts being biased to extend outwardly; (c) a filtercoupled to at least two of said plurality of struts, said filter beingadapted to filter material from a blood stream; and (d) means forpreventing said plurality of struts extending outwardly until saidfilter is to be deployed into a blood vessel.
 21. A filter device asrecited in claim 20, wherein each strut of said plurality of struts isadapted to extend outwardly away from a longitudinal axis of said lumen.22. A filter device as recited in claim 20, wherein said means forfiltering comprises a filter, said filter comprising a plurality ofpores.
 23. A filter device as recited in claim 20, wherein at least oneof said plurality of struts is biased toward a longitudinal axis of saidlumen.
 24. A filter device as recited in claim 20, further comprising atleast one radiopaque marker.
 25. A filter device as recited in claim 20,wherein a portion of said guide member is made radiopaque.
 26. A filterdevice comprising: (a) a guide member comprising a distal end, aproximal end, and a lumen extending from the distal end to the proximalend; (b) a strut assembly coupled to said distal end of said guidemember, said strut assembly comprising a plurality of struts, at leastone of said plurality of struts being biased to extend outwardly awayfrom a longitudinal axis of said lumen of said guide member; (c) afilter coupled to at least one of said plurality of struts, said filterbeing adapted to filter material from fluid flowing in a fluid streamwithin which said filter is disposed; and (d) a restraining membersurrounding at least one of said plurality of struts and said distal endof said guide member, said restraining member being adapted to preventsaid plurality of struts extending outwardly and subsequently releasesaid plurality of struts when said filter is to be deployed into thefluid stream.
 27. A filter device as recited in claim 26, wherein saidfilter comprises a plurality of pores, at least two of said plurality ofpores being differently configured one from another.
 28. A filter deviceas recited in claim 26, wherein said filter comprises a plurality ofpores, wherein each of said plurality of pores is sized in the rangefrom about 50 microns to about 300 microns.
 29. A filter device asrecited in claim 26, wherein said restraining member is adapted to bemoved in a proximal direction to enable said plurality of struts toextend outwardly.
 30. A filter device as recited in claim 29, furthercomprising an actuating member coupled to said restraining member andextending substantially to said proximal end of said guide member, saidactuating member being adapted to move in the proximal direction to movesaid restraining member in the proximal direction.
 31. A filter devicefor percutaneous insertion into a blood vessel during a procedure, thefilter device comprising: (a) a guide member comprising a distal end, aproximal end, and a lumen extending from said distal end to saidproximal end, said guide member being configured to act as an exchangeguidewire; (b) a filter assembly coupled to said guide member, saidfilter assembly comprising a filter adapted to filter material from ablood stream and a plurality of struts; and (c) means for preventingsaid plurality of struts from extending outwardly to allow said filterto deploy into the blood stream in the blood vessel.
 32. A filter deviceas recited in claim 31, wherein each of said plurality of struts isbiased to open said filter.
 33. A filter device as recited in claim 31,wherein said filter comprises an open proximal end and a closed distalend, said proximal end being adapted to conform to an inner surface ofthe blood vessel.
 34. A filter device as recited in claim 31, whereinsaid filter opens in response to a force applied by the blood flowingthrough the blood vessel.
 35. A filter device as recited in claim 31,wherein said filter is fabricated from at least one of a woven meshmaterial, a braided material, or a film material.
 36. A filter device asrecited in claim 31, wherein said filter comprises a material comprisinga plurality of pores.
 37. A filter device as recited in claim 36,wherein each of said plurality of pores is sized in the range from about50 microns to about 200 microns.
 38. A filter device as recited in claim36, wherein a major axis and a minor axis of each of said plurality ofpores is sized in the range from about 50 microns to about 300 microns.39. A filter device as recited in claim 36, wherein a major axis and aminor axis of each of said plurality of pores is sized in the range fromabout 50 microns to about 210 microns.
 40. A filter device as recited inclaim 31, further comprising means for radiopacity coupled to at leastone of said guide member, said filtering, said plurality of struts, andsaid means for preventing.
 41. A filter device as recited in claim 40,wherein said means for radiopacity comprises at least one of (i) aplurality of markers fabricated from a radiopaque material (ii) aplurality of markers coated with a radiopaque material and (iii) aplurality of markers doped with a radiopaque material
 42. A filterdevice as recited in claim 31, wherein said filter assembly is integralwith said guide member.
 43. A filter device as recited in claim 31,wherein said filter assembly is a separate assembly coupled to saidguide member.
 44. A filter device comprising: (a) a guide membercomprising a distal end, a proximal end, and a lumen extending from thedistal end to the proximal end; (b) a filter assembly coupled to saidguide member, said filter assembly comprising: (i) a filter comprising aproximal end with an opening formed therein; and (ii) a plurality ofstruts coupled to said proximal end of said filter, each of saidplurality of struts being biased to open said opening; and (c) anactuating assembly coupled to said guide member and said filterassembly, said actuating assembly comprising: (i) a restraining membercooperating with said plurality of struts, said restraining memberapplying a restraining force to the plurality of struts to prevent theplurality of struts from extending outwardly; (ii) an actuating membercoupled to said restraining member and extending toward said proximalend of said guide member; and (iii) an actuating element coupled to aproximal end of said actuating member, said actuating element beingadapted to move in a proximal direction to release the restraining forceto enable said plurality of struts to extend outwardly.
 45. The filterdevice as recited in claim 44, wherein said actuating member is disposedin said lumen of said guide member.
 46. The filter device as recited inclaim 44, wherein said proximal end of said filter, when deployed, isconstrained against the vessel wall.
 47. The filter device as recited inclaim 44, wherein said guide member further comprises at least oneradiopaque marker.
 48. The filter device as recited in claim 44, whereindisposed upon a distal end of the at least one of said plurality ofstruts is a coiled tip.
 49. The filter device as recited in claim 48,wherein said coiled tip extends through an aperture in said filter. 50.The filter device as recited in claim 44, where said plurality of strutsare integrally coupled to said guide member.
 51. The filter device asrecited in claim 44, wherein said plurality of struts are separatemembers that are coupled to a distal end of said guide member.
 52. Afilter device comprising: (a) a guide member comprising a distal end, aproximal end, and a lumen extending from said distal end to saidproximal end; (b) an actuating assembly coupled to said guide member,said actuating assembly comprising: (i) an actuating member disposedwithin said lumen of said guide member; and (ii) an actuating mechanismcoupled to said distal end of said guide member and to said actuatingmember; and (c) a filter assembly disposed within said lumen andconfigured to be deployed by said actuating member, said filter assemblycomprising: (i) a filter comprising a proximal end with an openingformed therein; and (ii) a plurality of struts coupled to said proximalend of said filter and said actuating member, at least one of saidplurality of struts being biased to open said opening.
 53. The filterdevice a recited in claim 52, wherein said actuating member is disposedin said lumen of said guide member.
 54. The filter device a recited inclaim 52, wherein said actuating member is partially disposed in saidlumen of said guide member.
 55. A filter device as recited in claim 52,wherein said filter assembly comprises means for opening said openingformed in the filter.
 56. A filter device as recited in claim 55,wherein said means for opening comprises said actuating member.
 57. Amethod for operating a vascular filter device during a procedure,comprising: (a) inserting a filter device into the vasculature of apatient distal of a portion of a blood vessel to be accessed during aprocedure, said filter device comprising: (i) a guide member having aproximal end, a distal end, and a lumen extending from said distal end;and (ii) a filter disposed within said lumen at said distal end of saidguide member; (b) deploying said filter from within said lumen into theblood stream to capture material that is dislodged during the procedure;(c) retracting said filter until an open-ended proximal end thereof ispositioned in relationship with said guide member to prevent saidcaptured material from escaping from said filter; and (d) uponpositioning a capture catheter to enclose said filter, removing saidfilter device and said capture catheter from the vasculature of thepatient.
 58. A method as recited in claim 57, where said filter devicecomprises means for an actuating member coupled to said guide member.59. A method as recited in claim 58, further comprising actuating saidactuating member to deploy said filter.
 60. A method as recited in claim57, wherein retracting said filter comprises retracting said open-endedproximal end of said filter until said proximal end is in contact withsaid guide member.
 61. A method as recited in claim 57, whereinretracting said filter comprises retracting said open-ended proximal endof said filter into said lumen of said guide member.
 62. A method asrecited in claim 57, wherein deploying said filter comprises pushingsaid filter from said lumen.
 63. A method as recited in claim 62,further comprising expanding said proximal end of said filter to formsaid opening.
 64. A method for removing a vascular filter device,comprising: (a) following deploying a filter of a filter assembly from aguide member by moving an actuating member disposed within a lumen ofsaid guide member in a distal direction, retracting said filter until anopened proximal end of said filter is positioned in relationship withsaid guide member to prevent the captured material from escaping fromsaid filter; and (b) upon positioning a capture catheter to enclose saidfilter, removing said filter device and said capture catheter from thevasculature of the patient.
 65. A method as recited in claim 64, whereinretracting said filter comprises moving said actuating member in aproximal direction by moving an actuator element in a proximaldirection.
 66. A method as recited in claim 65, wherein moving saidactuating member further comprises moving said actuator element by-handto move said actuating member.